[OnePlus 5T  Questions & Answers] don_dolarson:
To begin with, the device was rooted with Magisk 18.1 flashed about 2 years ago, running stock OxygenOS Oreo 8.1. Recovery: TWRP-3.2.1-1-cheeseburger. Kernel: RenderZenith OP5T [OOS-O-EAS-V3.7.0]. This was the setup I was satisfied with and running in about a year (a total of 2 years).

However, after the first year, I've tried to update TWRP to version 3.3.1-20190908-0-codeworkx-signed-forcedecrypt-dumpling in order to flash and update to the newer OxygenOS Pie 9.0. Something went wrong after flashing the newer TWRP and I couldn't get into recovery anymore... all I saw was a black screen when trying to get into it. I haven't bothered about this since the system booted and worked fine, so I gave up on the 9.0 update and stayed on 8.1. I was able to use it like normal another year. Everything was running very smoothly until a couple of days ago...

The battery has discharged to 0% and the device shut off by itself. 30 seconds before the shutdown, the UI was much less responsive and a popup about the device turning off popped up. I've put it in charge the whole night and when I woke up in the morning... couldn't boot into the system anymore. Instead, the phone booted into the 'broken' recovery, with constant lit of light blue LED (started to lit a couple of seconds after booting, only in the 'non-visible' recovery), and a black screen. I've looked up the fastboot/bootloader keys combination and went into it, well from there, I've tried the turn-off, start, recovery, and bootloader option. Turn off = Off. Start = Recovery. Recovery = Recovery. Bootloader = Bootloader.

The next step I've done was to connect it through a PC and run ADB on it in order to flash the old TWRP-3.2.1-1-cheeseburger. Re-booted into recovery straight after successfully flash and the recovery started to work again. The light blue LED stopped to lit any longer and I haven't seen it anymore. The first thing I've done in recovery was to clear the cache, dalvik, and do a nandroid backup, then tried to re-boot into the system. Finally, it booted into the system and I was happy like a kid when I saw the OnePlus boot animation again, however after putting my password and SIM pin code, I can enjoy it without any issue for about 30-40 seconds before the UI suddenly starts to be non-response (touch doesn't work), the screen starts to flash, sometimes (looks more like turning the screen on and off), until I see a "Turning off..." popup 20-30 seconds later (the battery is fully charged and disconnected from the power source) and the device is rebooting itself into the 'working' recovery. This is how it works each time I boot up into the system now. However, the power button is working and I can turn the screen off and on while the screen/touch isn't responding, the power menu can be opened by holding it (before it's too late and the "Turning off..." popup appears), from there I can choose to re-boot or power off. Magically the touch is working here. If the phone has been rebooted/turned off manually, by hitting either reboot or power off in the power menu, it reboots into the system instead and the same **** happens - not to recovery like it does when the "Turning off..." popup appears and it's turning off by the system.

I'd like to get everything back if possible, at least for one or two days, to back up all data, do some screenshots, back up browser bookmarks, history, open tabs, sms and calls, then give a fresh custom 11 to it.

Any help I can get from you guys? Is there a solution that I could try? What about flashing the newest Magisk onto it? Might it help or rather corrupt it more? Anything else? I'm out of knowledge in this situation and I'm relying on you.