[One (M8) Q&A, Help & Troubleshooting] MisOly:
The whole story is long, I will try my best to tell from the start.

About 10 month earlier, I got this 2 years old m8. I tried to root it. Yes, so I got online and found the only way was to flash a TWAP recovery, and flash a costom ROM. I did it and it worked fine for a month or so. Then for some reason I did a factory reset and power it off and threw it in the bottom of the drawer. (Dont want to say that I updated the system to something like marshmellow, I know now I should not use system updates on roma.it failed, sent me to hboot or recovery everytime)

Months later I tried to charge it and it just booted me to recovery everytime I tried to power it on. Or it was more like this: While chrging for some long hours, I pushed down the power key for like normal time and it did not respond. However after about 20 or 30 minuites it booted to recovery randomly. It just turned itself on. But when I selected reboot in recovery, it powered off right away and did not respond again. I did some combinations of power key, volume up and down and it was still dead. Then I used the same way(micro SD card) to flash a new rom when I caught it in recovery mod. It turned on about a minute after the flashing process was done. It worked again.

About a months ago when I was using it at about 15% battery it shutted off suddenly. I though it was a battery drain and I set it on a wall charger for a night. The next morning I remember it was still dead but did not notice if the orange light was flashing or not. I contacted HTC support and they told me to reset battery charing logic by holding all three keys for 2 minutes. It just failed. But some time in the day it power up again, right to the home screen. Then I found out the phone did not start up in regard to holding power key, instead it just turn on at times it felt like to. This happened when I disabled the fastboot option in settings>battery. I though a older android version would be more stable and download a 4.4.4 on sd card. Flashed it and it took some time to power on, ten minutes? Then the problem came, first it says google play service has stopped, then it says cant install any apps because SD card mounted improperly (something like SD card reading failed) or storage is full. I am sure my storage is quite empty and tried take out the chip and reinsert it. No use.

I then long pressed the power off option to boot into safe mode. It turned off then, nothing happened until about 20 minutes laters it booted up, to safe mode, just as if it wanted to.

Then there I finished download and install some apps through play store. Though it still reported the google play service has stopped message periodically. I then clicked on the restart option and...

It turned off... Never turned on again... I tried a to hold those three keys as long as I could, I did put it on charger for long times and its charging light gave me that short flashes, some times 6 seconds long flshes when use another charger. Sometimes it heated up while charging like this and sometimes cold like a stone on the same charger. I never stopped trying key combinations when time was available. And while on a charger about a week ago, it just randomly boot to recovery again(it showed only 2% battery, I charged it for so long...) I flashed the same ROM again this time, in addition to wipe data, delvik cache, I wiped system too:crying:, too excited. It said installation success and I selected reboot...

Dead... Like before... Only charging light flashing, some unknown alien codes... No response to keys... Computer recognizes as Qualcomm 9008 something(only shows periodically, came and gone in short intervals)...

It is now on charger, silently.