[One (M7) Q&A, Help & Troubleshooting] Whitestrake:
Hey, thanks for clicking my post. TL;DR Since updating from ARHD 40.3 to Viper One 6.2.0, my radio has been having major intermittent issues. I have a HTC One m7_ul unlocked outright from Optus here in Australia. It is as of right now running the latest firmware linked to by the Viper One/ARHD threads, the latest TWRP, is S-OFF and superCID, running Viper One 6.2.0.

Symptoms:

1) No signal most of the time.

2) Signal appears to return during periods of movement (e.g. driving).

3) Even at full signal, there is no mobile connection (no data, no text/calling).

4) Once every few hours, when it has signal, it will gain mobile connection for a short period of time, after which it will cut out again - repeat to 1).

Here's a short story about how this came to be:

For many many months now it has been running just fine on stock firmware, rooted with S-ON running ARHD 40.3 (since that version came out).

About a fortnight ago I started noticing issues with my contacts application. Something to do with 501 contact link suggestions and certain contacts having hundreds of Facebook profile entries. This would cause issues in the People app (people just wouldn't load) and the SMS app (message histories wouldn't load, including new texts).

After some troubleshooting attempts, I resolved to reinstall a ROM. I opted to install the latest Viper One (6.2.0) successfully. It resolved my issues. However, it introduced a new one. The next morning I woke up to 4 texts from my service provider informing me I'd missed calls. I had no notifications as such, so the calls never reached my phone. I put it down to tower signal flex in my area. I left and as I walked out the door I noticed I had no signal (no bars, x above the icon in statusbar). Driving around seemed to fix the issue though, it got back up to normal values quickly enough.

However, even though I had plenty of signal and mobile data was ostensibly turned on, I couldn't get internet. I tried sending a text to myself but it failed send. Calls out simply waited on signal and then timed out. Every single other function of the device is 100% AOK (wifi, bluetooth, nfc, etc). The entire ROM is fully functional, can't find any other issues with stability or otherwise.

I put up with it for the day and get home and start troubleshooting. Here's what I tried so far, in order:

1) Change from Viper One to latest ARHD (71.1). Installed with no issues. Booted phone, no dice - no signal.

2) Checked SIM by moving to old iPhone 4 - full signal, radios work. It's not a service issue.

3) Revert to last known working ROM - ARHD (40.3). Installed with no issues. Booted phone, no dice - no signal.

4) Research research research. Think it might be a problem with firmware perhaps. Tried revone, failed because I'm not on 4.2.

5) Flash MaximusHD (11.0.0) in order to make use of revone for S-OFF/superCID. Flashed latest firmware linked in Viper One/ARHD threads.

6) Reboot phone. Still no dice with latest firmware on MaximusHD (11.0.0).

7) Retry with latest ARHD. No dice.

8) Retry with latest Viper One. No dice.

In every single instance, all the ROMs are fully functional except for mobile signal - wifi, bluetooth, nfc, etc. radios function perfectly. No issues with ADB or fastboot during any step of these processes. All my device info shows what I expect to see. I've searched as much as I can, to no avail. I turn to first-time posting here as a last resort to maybe find out what the issue is.

I am slowly reaching the thought that the hardware itself might be the issue. I'd appreciate any insight into what could be causing this - be it software or hardware - as well as if there is any way to test or diagnose the radio physically. Even just a confirmation ("Yep, sounds like your radio's FUBAR"). In the meantime, I'll be using aforementioned iPhone 4 (ugh).

Thanks for reading.