[Moto Z2 Play  Questions & Answers] sthiag0:
TL;DR

Moto Z2 Play - XT1710-07

The phone recognizes the SIM card but there is no signal (no service). Tried several things, including flashing a custom ROM. I'm considering buying a new motherboard and changing it myself, but first want to know if anyone knows more about this issue or has an idea/suggestion.

Edit: As an added bonus, something that only now I realized. Now when I charge it, it gets EXTREMELY hot. Like I-can't-even-use-it hot. I used to use the phone while charging all the time, but now I can't even hold it. Seems like the problem is when it tries go past 80% charge. It gets super slow, keeps trying and gets hot. Now I don't know if it's a software problem caused by the various flashings or if it's something that would remain even after swapping the motherboard.

Edit 2: I did a full discharge of the phone and recharged it while turned off. It seems to have normalized the battery problem

Edit 3: RIP. I tried to remove the screen before deciding about buying a new board. In the process, I ended up tearing the digitizer flat cable apart. Now I don't think it's worth it buying both a new screen and a motherboard.

The full story and things I've tried

My phone was working all nice and dandy until it stopped having signal/service. Wifi works normally, but anything related to the SIM card doesn't, like phone calls or mobile data.

A list of things I've tried somewhat in order (both of time and of complexity):

* My SIM in another phone: it works normally, so the problem is not the SIM itself

* Another SIM in my phone: it doesn't work, so the problem is definitely the phone

* Using the second SIM slot

* Changing "Preferred Network Type" between the available ones (4G, 3G, 2G, including Enhanced 4G LTE Mode on and off): this one and the next two items don't really make sense to me, since these options seem to be only related to mobile data (4G/3G internet) connection, not to phone calls which is also not working, but I tried them anyway

* Manually selecting the network: Errors with "Selected network unavailable" and, after trying to register for a while, toasts another error saying "Can't connect to the network, try again later"

* Manually selecting the APN: Tried both selecting between the two options available and manually adding an APN by googling the correct info for my carrier

* Simply booting into fastboot and restarting bootloader: a video on YouTube claimed that it was a temporary solution and that I'd need to do it every time it lost signal. But it didn't even work the first time

* Disabling CQATest and then restarting bootloader (and also clearing its data/cache and removing its permissions): a lot of videos on YouTube claimed this was a solution, including for other Motorola phones. Apparently CQATest prevents the phone from working properly in some scenarios. But I think only when you de-google your phone? Not sure. All I know is that it didn't work either

* Using the phone connected to the wall charger: I think this was another YouTube suggestion, and it actually worked for a few minutes. But I guess it was just a coincidence, as it never worked again

Now for some more... "forceful" attempts:

* Factory Reset: Not sure where I saw this suggestion, but it was pretty much the next logical step. Gathered courage, backed up all my data, etc, aaand... nothing again

* Flashing another ROM: Guess it was here at XDA that I read that it was a problem with Motorola's stock ROM. That, paired with my belief that it could still be related to CQATest being installed, I again gathered more courage to flash a custom ROM. I chose LineageOS and found out that it was no longer supported, but decided to install the last official release. I also read that the problem was the Pie modem firmware, so it all seemed to be going fine since the last official release is Oreo 8.1. I flashed it and BAM it worked! ... for a few minutes and never again. I messed around with LineageOS, tried some of the previous things again, but nothing.

Then, I tried to restore my TWRP backup but it didn't work. So I searched a bit more and downloaded the Stock Pie ROM, flashed it, and closed the bootloader. And then I realized the restore probably didn't work since my backup was made using Pie and my phone was on Oreo. Maybe some files/partitions were missing? Also, when I was creating my TWRP backups, I tried creating a full system image backup but it kept erroring. Only later I realized the problem was that the USB Drive was FAT32 and the full system image was bigger than 4GB. Oh, well, now I know.

So now that I'm with my phone pretty much back on square one, I take it to an authorized repair shop. The clerk said that it was a common problem, and that sometimes it could be solved "by software" and that they'd try that. The other option was to change the whole motherboard, which they didn't do because it was "not worth it" and "almost the full price of a new phone". After two days, my suspicions were confirmed: they didn't fix it with their "by software" attempt. At least I didn't have to pay anything.

When I got the phone back, I put the SIM in again and it showed the icon as if there was signal. But when I tried to call someone, the signal disappeared again. I tried searching a bit more, went through all pages of Q&A here at XDA forums and there were like 3 posts regarding loss of signal. All without any response. On YouTube, I found some videos offering a suspicious .bat file. Upon inspection, it merely erased the modemst1 and modemst2 partitions and then wiped user data and cache. I tried it, nothing to lose. Also didn't work.

Now I'm contemplating a few options:

By watching some disassembly videos, I saw that, when opened, the phone has some parts that act like antennas. I thought that maybe those were not properly connected to the board? Maybe they got dislodged during a fall? Seems unlikely tho, since they are screwed in. I searched for a new motherboard to buy and it's a reasonable price. But I'm afraid it'll have the same problem (or develop it in a short time) since I can't find anywhere what the true cause of the problem is.

Another option is to just give up, buy a new phone and use this one as if it was a "small tablet" lol

So, do you guys have any other suggestions or ideas as to what might be the problem? Maybe a tip like "solder a wire to this spot to create a make-do antenna"? I don't really know where else to search.

If not, thanks anyway for those who read it all (: