[General Questions and Answers] Imminent-darkness:
Apologies for being a member of this forum for so long and making this my first post. Regardless of this being my first post, these forums have been a life saver many times, and I would like to thank the very knowledgeable people who frequent these forums for all the time, effort, and patience that the put into new development and answering questions for those like me, who have a lot to learn yet.

Now to my issue...

I have had my OnePlus 7 Pro (Global) for a couple weeks now. It is on Android Pie, and I intend on keeping it on Pie for a while. I rooted it straight out of the box with Magisk 19.3 and TWRP 3.3.1-4 (Guacamole)(Installed by zip to both partitions) and it has been working great. No problems at all.

Two things have changed today, so I'm not sure which is the issue, if either are. One is that I updated to Magisk 20, and the other is that I tried to boot into recovery with and OTG cable attached with a 256g sansdisk flash drive attached to that. This is when it booted into bootloader instead of TWRP.

I disconnected the OTG cable and rebooted into system. I still had root from Magisk, so I attempted to reboot into recovery again, only to find that I booted into the bootloader again. Now I figured that I had lost TWRP, so I hooked my phone up to my windows 10 computer to flash custom recovery once again. I had read that it is possible to install TWRP to the ramdisk now through advanced settings, so I booted into temporary TWRP and selected the TWRP.img file to install to ramdisk. The command line said it was a success, so I backed out of that screen and rebooted into recovery. Once again, I was booted into the bootloader.

I disconnected my phone and booted into system. I still had root and everything was working as usual, so I reconnected my phone again and tried to install TWRP to both partitions as I did originally. The terminal went through the process rather quickly (usually it takes a minute or so to install TWRP), but claimed it was a success and that I lost root, like it should. I backed it up a screen, reboot to recovery.. no dice.

I've tried to take Magisk back to 19.4, but it didn't effect whether TWRP would stick.

I have a TWRP backup that I took of everything a couple days ago. I thought about trying to restore and see if that works, but I wanted to run it by you all to see if maybe somebody else has had this issue.

Could the attempt at rebooting into recovery while connected to OTG have done this?

Thank you all in advance for the assistance. I'm aware that this post is long winded, but I am also aware that you all like as much info as possible.

Thanks.

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Update

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My phone is working now, but not before I massacred it. I attempted to restore with that twrp backup I had while temporarily booted into twrp, through the twrp.img, through adb. I had it on the phone, so I figured I could use it.

I don't know if it was a corrupted backup, or if the process wasn't orthodox enough, but the restore crashed in the twrp terminal. I tried to boot into system and found that I had bricked the phone.

I ended up having to use the msm-downloadtool that I found here on xda. It was a lifesaver for sure.

Anyway, I figured that I'd update this thread. My phone is completely reset, bootloader unlocked, rooted, with custom recovery once again. I'm not sure what the cause was for the initial issue. I would still be interested to hear of any theories.