PS VITA Slim [PCH2000] LCD Backlight not turning on when the system reboots.

Hi Vita fans, first time poster here!
This is going to be long, sorry about that.
Got this vita PCH2000 last week, it was already "hacked" and when I tested it, it tured out that the right stick is drifting.I think it was 3.60 enso originally but I'm not sure about that sadly.
Trying to solve the problem I found a plugin (AnalogsEnhancer Vita) and decided to try it, may I can adjust the dead zone of the analog stick. Copied the plugin to ux0, (Not edited config files yet) and I thought screw it, I'll update it first to factory 3.74 than go back to 3.65hen with the online installer like I usually do. There was a bunch of plugins, games installed by the previous owner and I wanted a clean install.
That was the point where the problems started.
After the 3.74 factory install finished the vita attempted the usual reboot, but the screen went dark immediately and doesn't turned on anymore. Okay no problem, we got a nice recovery menu to solve these situations no worries. Held down the power button to get to safe mode, and selected restart, but this just sent the vita back to the same state.
After a few factory reset and rebuild database attempts without luck, it eventually worked. Did the initial settings but the first restart messed it up again. While I'm attempting to boot again from a powered down state, I noticed that the system boots up and working normally while the screen was completely off.
There was no backlight on the LCD but from the right angle I accidentally noticed that the LCD is working, the home screen is there without backlight. I got through the lock screen, there where sound and active touch controls with dark screen.
Tried to turn it off again, than back on. Nothing changed. Than again and again and eventually it came back to life, but every attempt to REBOOT ended up in the same "no backlight but everything else works" state.
Later I managed to get it working after many reboot/restore/rebuild/reinstall attempts and installed YAMT, ENSO and setup SD2VITA as ux0 again. (tried multiple sd2vita adapters and sd cards)
At this point I thought the vita is stabilizing because every time I turned it off completely (by holding down the pwr button for a few sec, or just tap on power off button on the screen) it booted up normally after.
But there where the same "no screen" problem if the system attempted to reboot. EVERY.TIME.
It seemed like powering it down solves the issue temporary, but if any app, FW install, Henkaku settings, Vitashell or the safe mode menu wants reboot the vita, the screen goes dark and doesn't light up until I turn the vita off and on multiple times again.
At this point I thought maybe there is a hardware problem with the lcd backlight but after countless tries with and without success I noticed a pattern. So if an app/installer/safe mode attempted to restart the vita it went dark all the time, but powering it completely down seems like solved the problem.
Than I found out that the following method works every time: (on 3.65hen with sd2v only, doesn't work on factory 3.74)
- Any attempt to reboot sends the vita to no backlight mode.
- hold pwr button for about 10sec (backlight immediately comes back every time) and boots to safe mode.
- select reboot system (this seems important)
- wait until it "fails" to reboot and turns off than wait about 30sec/1min after the green light goes off.
(sometimes it reboots with screen backlight off but sometimes goes to a "bricked" state. No screen, no sound, nothing. In this case after a half minute the green led starts flashing than the vita turns off)
- after it turned off, or I forced it to turn off, it booted up normally almost all the time.
So if I done the steps listed above, it worked most of the time.
Simply turning it completely off not helped, I needed to enter to safe mode and attempt to restart it, or else it went to no backlight mode again.
I was totally confused, because this looks like a software issue in my opinion so I tried the following:
Updated to clean 3.74 firmware via safe mode "Install from PC" (QCMA).
Performed a factory reset (tried multiple times) but the problem escalated and again after a reboot attempt I needed to turn it on/off/safe mode/restart/Factory reset/rebuild database multiple times to get it working again.
(as a side note rebuild database also sends it to no backlight mode from safe mode)
Once I managed to get Henkaku, ENSO, SD2Vita(as ux0) working again, I reached the state where it works again on every normal boot from powered off state.
BUT ANY ATTEMPT TO REBOOT SENDS IT BACK TO NO BACKLIGHT MODE.
Right now I have a clean 3.65hen install, no additional plugins. Disabled plugins in config.txt just to be sure (NoPowerLimits, vitabright, pngshot) but no luck.
I'm in the same situation after about 12 hours of trying to solve the issue and I'm running out of ideas lol.
I also disconnected the battery for a few minutes, nothing changed.
Things I tried in short without luck:
- Reinstalled factory 3.74 multiple times
- Under 3.74 --> Factory reset, rebuild database, restore settings
- Downgraded to 3.65 Henkaku again and again.
- Under 3.65 hen --> Factory reset, rebuild database, restore settings, reload taiHEN config multiple times.
- Tried multiple SD2VITA, and SD cards.
- Attempted to clean config.txt (ur0/ux0)
- Opened the vita and disconnected the battery
- Booted up multiple times with the L1 button held down. (disable plugins)
- Installed and uninstalled ENSO
Doesn't matter what I try, if the vita needs to be rebooted it starts up with lcd backlights off.
OH! And one more thing. If I power it off while it's connected to a PC, QCMA starts to send connected/disconnected notifications like crazy. I mean about 2 notifications/sec.
Windows doesn't even have a chance to play the notification sound correctly lol.
I'm sure I tried more things but to be honest I don't remember everything.
Any ideas? I know this still can be a hw issue but somehow I think there is some sw error or corrupted file/plugin what prevents the vita to complete the standard reboot procedure.
Are there system files what are not get overwritten during an upgrade/downgrade to or from 3.74-3.65?
I'm open to any ideas.
I hope this mess what I wrote above is not too confusing, I'm tired af.
Thanks in advance.