TLDR: unable to unlock bootloader when on fastboot mode, through web install. I get message: Error: Bootloader was not unlocked, please try again!.
I've been on grapheneOS since day one. Few months back my phone, on occasion, started hanging and rebooting itself at random times (when opening an app etc.). I initially thought this was just some minor software glitch. Normally it would just restart and everything would be fine. Then it started going on bootloop and required many cycles to resume. But recently it started to happen more often, and the last few times it would require me to sideload a newer version just to get out of the bootloop. I'm almost certain that this might be a hardware memory corruption issue. It happened again this time where it wont even let me sideload a new version as it would just crash. Then I even performed a factory reset. That did not work either. I now want to bring it into a service center, but before that i want to revert back to stock android otherwise i'm almost certain they will refuse to honor my warranty.
But in order to do this i must unlock the bootloader and remove non-stock key, which I'm unable to do. My process: