[Xperia Z1 Q&A, Help & Troubleshooting] BOplaid:
Well, I got hold of a microUSB cable that supports data transfer (checked with (barely) working Galaxy S5) and I connected it to the Z1.

And it just keeps connecting and disconnecting. At least with the cable that didn't support data transfer, when I plugged it into my laptop, it at least charged the phone. But here it just connects and disconnects from the phone. Here's a bit of Flashtool log:

17/47/2024 19:47:18 - INFO - <- This level is successfully initialized

17/47/2024 19:47:18 - INFO - JAVA_HOME : f:\flashtool\jre

17/47/2024 19:47:19 - INFO - Flashtool 0.9.36.0

17/47/2024 19:47:19 - INFO - Searching for a web proxy

17/47/2024 19:47:21 - INFO - A proxy has been found. Using it as default

17/47/2024 19:47:21 - INFO - Syncing devices from github

17/47/2024 19:47:21 - INFO - Opening devices repository.

17/47/2024 19:47:22 - INFO - Scanning devices folder for changes.

17/47/2024 19:47:39 - INFO - Pulling changes from github.

17/47/2024 19:47:41 - INFO - Devices sync finished.

17/47/2024 19:47:44 - INFO - Loading devices database

17/47/2024 19:47:44 - INFO - Loaded 137 devices

17/47/2024 19:47:44 - INFO - Starting phone detection

17/47/2024 19:47:58 - INFO - Device connected with USB debugging off

17/47/2024 19:47:58 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/48/2024 19:48:20 - INFO - Flash canceled

17/48/2024 19:48:29 - INFO - Device disconnected

17/48/2024 19:48:52 - INFO - Device connected with USB debugging off

17/48/2024 19:48:52 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/49/2024 19:49:38 - INFO - Device disconnected

17/49/2024 19:49:40 - INFO - Flash canceled

17/50/2024 19:50:40 - INFO - Device connected with USB debugging off

17/50/2024 19:50:40 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/50/2024 19:50:49 - INFO - Device disconnected

17/06/2024 20:06:23 - INFO - Device connected with USB debugging off

17/06/2024 20:06:23 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/10/2024 20:10:09 - INFO - Device disconnected

17/11/2024 20:11:13 - INFO - Device connected with USB debugging off

17/11/2024 20:11:13 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/11/2024 20:11:17 - INFO - Device disconnected

17/12/2024 20:12:28 - INFO - Device connected with USB debugging off

17/12/2024 20:12:28 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/12/2024 20:12:33 - INFO - Device disconnected

17/12/2024 20:12:44 - INFO - Device connected with USB debugging off

17/12/2024 20:12:44 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/12/2024 20:12:55 - INFO - Device disconnected

17/13/2024 20:13:39 - INFO - Device connected with USB debugging off

17/13/2024 20:13:39 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/13/2024 20:13:49 - INFO - Device disconnected

17/35/2024 20:35:53 - INFO - Device connected with USB debugging off

17/35/2024 20:35:53 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/35/2024 20:35:58 - INFO - Device disconnected

17/56/2024 20:56:48 - INFO - Device connected with USB debugging off

17/56/2024 20:56:48 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/57/2024 20:57:01 - INFO - Device disconnected

17/57/2024 20:57:21 - INFO - Device connected with USB debugging off

17/57/2024 20:57:21 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/57/2024 20:57:30 - INFO - Device disconnected

17/26/2024 21:26:55 - INFO - Device connected with USB debugging off

17/26/2024 21:26:55 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/27/2024 21:27:03 - INFO - Device disconnected

17/27/2024 21:27:21 - INFO - Device connected with USB debugging off

17/27/2024 21:27:21 - INFO - For 2011 devices line, be sure you are not in MTP mode

17/27/2024 21:27:43 - INFO - Device disconnected

The reason why there are time gaps between them is because I unplugged the phone a few times to see if I can solve it myself. Which obviously failed.

And I know it's not the cable or the laptop, because it works perfectly fine with my Galaxy S5.

I finally don't need to use that hard drive cable anymore for the S5...