I don't actually need any help right now anymore but I couldn't let this go and I wanted to post just in case it happens to anyone else, as well as get some council on wtf just happened. Sorry if this is actually a normal or benign thing to happen. My user account suddenly stopped accepting my password mid-session while I was trying to install something (never installed it). Of course the first thing I thought was that I'm typing too fast and messing up the inputs however I wrote it out slowly over and over. It got to the point where I wrote it in plain text in a text editor to copy and paste over, thinking I must be having a brain fart. It still rejected it.
So thinking it's some sort of serious RAM or cache issue I rebooted my computer... and couldn't log back in! At this point I was quite worried, heart racing in fact. Root user was also not working. Completely locked out of my computer. I managed to chroot in using a live USB of Manjaro and then reset the root password. I then logged in as root on the non-live system and set the user password back to what I always use.
I'm honestly bewildered at what just happened and still a little concerned actually in case it was some kind of attack although I understand that's incredibly unlikely. The last few things I were doing of note were
- Playing DOS games (Star Trek 25th Annivesery)
- Trying to set up Open Morrowind
- Using pacui's 'maintain system' feature
Posting my specs just in case they're relevant