[ONE Q&A, Help & Troubleshooting] RIP_A0001:
I may have found a solution/work-around to the problem described (in case anyone's still trying to unbrick a OPO after all this time). I must warn, however, that I really have no idea what I'm doing as I'm new to all of this, and have blundered through with no real understanding of what's going on, so pay heed at your own risk. It uses Qualcomm's QFIL program and Zyxxeil's OPO unbricking tool. I want give detail in describing the steps involved, so this will be fairly long.

***background***

My 64GB OPO has for the past couple of months almost always failed to get past the first 6-7 seconds of booting, and powered off before reaching the Cyanogen animation. It did the same when booting into fastboot and recovery, and at some point it stopped being able to access recovery at all. Very rarely it would boot, but pressing the power button while it was on would cause it to crash a few seconds later. I discovered that it would consistently boot properly if volume up were tapped while holding down the power button before it vibrates and the OnePlus logo appears, but this fix simply stopped working recently, and so it became impossible to turn the OPO on. Before giving up on it, I decided it would be worth trying the hard unbricking tool based on the ColorOS installer by Zyxxeil. However, I had the problem where the tool continually repeats the step of flashing 8974_msimage.mbn without progressing any further, to which nobody ever seemed to find a solution. I may have found a way to get around the problem, however.

Even though the procedure seems to have worked, the phone still shuts down after a few seconds as it did before (so I suspect my device has a hardware problem, possibly with the power button, and there's nothing that can be done for it). This means that I can't confirm that the fix actually works, but only that it appears to have worked. What it did was:

1) unbricked the phone - it probably wasn't even bricked before, but it definitely was after the installer hung on 8974_msimage.mbn ; it wouldn't respond to the power button at all afterwards. Applying the workaround allowed it to show signs of life again.

2) installed the COS11 fastboot. I'm not sure and can't tell whether the rest of the OS is there or intact, but the fastboot logo has changed from the newer small one to the bigger one from older versions.

***the problem***

The standard method for dealing with a hard-bricked OPO is to use the ColorOS tool as described in the "[GUIDE] [UNBRICK] Unbrick Oneplus One" thread and then flash Cyanogen, or to use Zyxxeil's tool which goes straight there. A common issue in both is that after pressing start, the tools repeat the step of flashing 8974_msimage.mbn , seemingly disconnecting the phone each time, and never progressing beyond that. This happened to me as well. This will happen if the tool is not run as an administrator, but for some people the same problem is seen even if it's run as an administrator. To the best of my knowledge, nobody has posted a solution to this problem, but some have suggested using alternative methods such as using QFIL (which I have gotten to work) or MiFlash.

***potential solution***

From what I understand, QFIL does the same thing as the unbricking tool, only not automatically. I directed it to use the files provided by Zyxxeil's tool, and it was then able to do something that unbricked the device as described above. This is what I did: (all on Windows 10, *not* using the original cable)

Required files:

1) Obtain the Qualcomm QDLoader driver. I used the the Qualcomm HS-USB QDLoader 9008 2.1.0.5 x64 driver from Zyxxeil's tool's thread (page 5, #48).

2) Download Zyxxeil's tool. I used the 64GB version. Extract DRIVER.iso and run setup.exe as described. I'm not sure whether this actually did anything and presume manually installing the driver in 1) overrides this, but I'm including this for completeness.

3) Download QFIL version 1.0.0.2 . I originally used 2.0.0.5 , but this did not work (it produced the error "unable to read packet header. only read 0 bytes", to which the recommended solution was to use an older version). This can be run from the extracted folder. Open it once, and then close it again - it seems not to behave properly the first time it is run.

Preparation:

4) Create a new folder, for instance on the desktop, and give it a short name. Copy and paste (or just move) the contents of the "OnePlusRestoreTool" folder from Zyxxeil's tool into here. This step is because QFIL supposedly doesn't like long folder names or locations (I'm not sure whether this is true or not but there's no harm in making sure).

5) Install the QDloader driver: (the PC may need to be disconnected from the internet for this stage, I think Windows may try to automatically download and install incorrect drivers)

>Open device manager, then plug the OPO into the computer. It should come up after a few seconds under "Ports (COM & LPT)" as something like QHSUSB_BULK or Qualcomm HS-USB QDLoader 9008. Mine originally showed up as "Quectel QDLoader 9008". If it comes up as a malfunctioned device ("Unknown USB Device") under "Universal Serial Bus controllers", try holding the power button on the OPO down for a few seconds, or holding it down for a few seconds at the same time as volume up. If it's still not recognised, try rebooting the PC and repeating this step.

>Right click on the device as it appears in device manager, select "Uninstall device", tick the box saying "Delete the driver software for this device", and click on "Uninstall".

>The OPO will disappear from device manager. Unplug and then replug it into the PC, and after a few seconds it should be recognised again, perhaps as "Unknown USB Device" again, requiring the same procedure as above. It should now show up as QHSUSB_BULK under "Ports (COM & LPT)"

>Right click on the device and select "Update driver", then "Browse my computer for driver software". Paste in the file path for the folder containing the driver as downloaded above, which will be called "20561190_ed08f7139a2028da454a6668162f44ac311facc0" if using the driver specified above. Ensure "Include subfolders" is ticked, and click on Next. This should install the driver, and because it's signed, it shouldn't present problems often encountered in this stage. Your device should now be called "Qualcomm HS-USB QDLoader 9008", with (COM#) after it.

Fix:

6) Restart the PC, leaving the phone plugged in. Open device manager again. At this point, if it is detected as a malfunctioned "Unknown USB Device", do not try to remedy it as described above - leave it as it is. This is exactly what happened in my case.

7) Run QFIL.exe as an administrator. I don't know whether this is actually necessary to run as an administrator, but seeing as problems arise in the normal methods from not doing so, it seems sensible. If the device is listed as "Unknown USB Device", then QFIL should say "No Port Available".

8) In QFIL, click on "Browse" in the "select programmer" section. Navigate to the folder where the contents of Zyxxeil's tool were copied/moved to, and open "prog_emmc_firehose_8979.mbn". Lower down, click on "Load XML", which should give you three files to choose from. As I couldn't fully boot my OPO afterwards I don't know which one is most appropriate, but I have tried the procedure with each and it worked for all of them. Perhaps start with rawprogram_unsparse.xml and if that doesn't work try the other two. Click Open, then select patch0.xml , then click Open again.

9) Paying attention to the QFIL window, hold down power+volume up until the text changes from "No Port Available" to "Qualcomm HS-USB QDLoader 9008 (COM#). Incidentally, this will also cause the device to change from "Unrecognised USB Device" to "Qualcomm HS-USB QDLoader 9008 (COM#)" in device manager. I believe that this step starts "Qualcomm's debugging mode" as explained in Zyxxeil's thread, and this is necessary for the process to work.

10) Click on "Download" (below "Load XML"). QFIL should do its thing, and if nothing has gone wrong the phone might be unbricked at the end of the process. Disconnect from the PC and see if it works.

In my experience, where this step did not work it gave one of two errors:

"unable to read packet header. only read 0 bytes" - this happens on the newer version of QFIL, which is why I used the older one.

"unable to download flash programmer using sahara protocol" - this was the troublesome one. I believe it means that the phone is not in Qualcomm's debugging mode. This would probably be the case if, for whatever reason, the PC recognised the phone immediately as Qualcomm HS-USB QDLoader 9008, and so it wasn't necessary to hold power+volume up for the PC to recognise it properly. In my case the program ran properly the first time but was interrupted because I hadn't transferred all of the right files to the target folder. After I had done this and tried again, it gave this error. I fixed this by holding down power+volume up, while the device was recognised, until the PC made a sound indicating something had been plugged in. The next attempt to download was successful.

If the procedure doesn't work properly, it might also be worth using one of the other two XML files mentioned in step 9.

*** ***

Anyway, after hours of searching and trial and error, this unbricked the phone, with it becoming responsive once more to button presses, despite still having the original problem of powering down during boot. It seems to have the CM11 fastboot as expected, and I was able to have my PC recognise it in the short time it stays on using fastboot devices. Other than that, I'm afraid I don't know how successful this was, or how successful it would be for other people. I hope this is useful nonetheless!