Color me SOL.
My Moto Z has been exhibiting a similar issue. It would heat up very easily on even mundane tasks, thermal throttle HARD and stay there until I leave it to cool off before very easily doing do again, at which the phone is already past the point of being uncomfortable to hold. It...
About 4 months since, and HDR+ never fails to amaze.
I do wish the app gave exposure compensation controls, though. I often found that it landed too bright at times.
It's an issue on NPL25.86-15, as the 2 cores go to sleep completely, causing performance to suffer.
In this case, it's more of a reading issue, as the processor works just as intended unless you've tweaked the governor.
Another weird anomaly is that the battery gauge seems to go down at a...
I thought I'd say something odd about this kernel.
After a while, AIDA64 and CPU-Z can't identify the big cores, identifying them as either "stopped" or "sleeping".
However, running benchmarks reveal that the big cores are indeed running, as it gets scores that are typical of other 820 devices...
Stock recovery.
I presume it's either because the build I ran was designed for a different region (same model code, though) or that the Marshmallow bootloader was incompatible with the OTA.
Regardless, it's been working fine for a bit, although one Busybox installer gave me a small scare when...
Just for background info, at the time it happened, my Z was running NPL25.86-30 from the following thread;
https://forum.xda-developers.com/moto-z/development/android-nougat-moto-z-versions-t3506342
It was running perfectly fine, then an OTA thing appeared. Well, I made the single big mistake...
Since you have the kernel, it should be a piece of cake to flash since dm-verity ain't messin' around anymore.
Also, can you verify that your 2 high-performance cores are indeed working? I just flashed NPL25.86-30 and it brought back proper functionality of those. Seems to run significantly...
I have a feeling that it might also be due to your phone running an older version of the software that the bootloader might not support.
Regardless, I'm really glad that your phone is working. Enjoy! ;)
Well, if it works, then we'll be golden.
But if it doesn't, I think the -30 firmware might help better.
Sadly, I'm about to log off for the day, so do keep us updated on how it goes. Fingers crossed that you can get your Z working again.