[Verizon Motorola Droid Turbo Q&A, Help & Troublesh] ChazzMatt:
Yes, some of your symptoms like the endless bootlooping seem very unusual. I don't know of radio-related issues that cause that. But not being able to use GPS, Wi-Fi connection issues, or even not detecting SIM cards are symptoms of radio/modem problems.

When flashing a custom ROM on our Quarks, GPS especially was a complaint. There were workarounds to fix it as early as 2015, but then [MENTION=5747496]bhb27[/MENTION] (who is the dev for several custom ROMs) came up with the [MENTION=5747496]bhb27[/MENTION] Clear Modem File. You flash that. In simplistic terms it clears the cache of your modem. It has helped countless people, with Droid Turbo/Moto Turbo/Moto Maxx.

Often just that fixes any issues, but you can also then take the next step of re-flashing the most current radio/modem for the Droid Turbo.

ROMs don't have radio/modems included inside the ROM. When you flash a custom ROM, it uses the radio you already have. Clearing the cache, and reflashing makes everything new again.

We've had custom ROMs for over two years now for our Quark phones. True the Droid Turbo XT1254 bootloader was finally unlocked back in November of 2015, but still that's been 1.5 years. ;) There's tons of custom ROMs and if you look at the download stats of those ROMs there's THOUSANDS of people using them. If the ROMs had the issues you had, there would be no users, believe me!

The issue is for a percentage of people, not even a majority, but a percentage, the radio/modem becomes confused when flashing a custom ROM. But it's easily fixed...

Go look at this page from just two days ago. Similar issue with AOKP 7.X. EXCEPT it's NOT an issue with the ROM. It's the issue of someone not reading thoroughly.

Phone calls not working

https://xdaforums.com/droid-turbo/development/rom-aokp-7-x-quark-t3504629/page67

Yet, the dev clearly says in post #2:

Once the user flashed that, all was well.

and this guy over in RR 7.x last week, with a Moto Maxx XT1225:

Wi-Fi won't connect.

https://xdaforums.com/showpost.php?p=71652207&postcount=1474

I helped him by providing the link to the clear modem file and the latest radio/modem for his model. (He flashed both, just to make sure.)

* Here's the Clear Modem File, also called the Clean Modem file:

[MENTION=5747496]bhb27[/MENTION] Clean_modem_status

https://www.androidfilehost.com/?fid=24531035584725320

*Here's the latest TWRP-flashable Marshmallow radio/modem for the XT1254 Droid Turbo.

*For those with the XT1225 Moto Turbo/Moto Maxx, here's the latest TWRP-flashable radio/modem:

XT1225 MARSHMALLOW Radio_Flasher_Stock_MPGS24.107-70.2-2.zip

https://www.androidfilehost.com/?fid=457095661767122577

Do NOT flash an XT1254 radio over an XT1225 or an XT1225 radio over an XT1254. I am including both radios in this thread for people who may need them.

The clear modem file/clean modem status file (whatever you want to call it) is for ALL Quarks, but the radio/modem files are very device specific.

I always keep a copy of the Clear Modem file and the latest TWRP-flashable radio in my Download folder on my phone. Whenever I flash a new ROM or even an update to a ROM, I always flash those files too. It can never hurt and can only help. ;)