This just happened on another one of my computers with BTRFS. I didn't run pacman or manually run any other installations or updates. This is on a vanilla ArchLinux machine I've installed KDE using archinstall a few months ago. I use this machine often and its the first time it happened on this machine. Perhaps Discovery or Flatpak ran an update in the background. I'm not aware of automatic updates being enabled though.
I have a problem when my computer where when I put it in sleep, or press the power bottom once, it automatically turns back on after sleeping / shutting down. I get frustrated with this sometimes and force shutdown my computer, either by holding the power button or pulling the cable. I know I shouldn't do this. Turning on my monitor, going into the UI, safely shutting down my computer can become very time consuming on my busy schedule. Its rare it happens, but life happens and I sometimes don't have time to wait a minute for my computer.
May I note when going through archinstall and choosing a filesystem, do we want BTRFS or EXT4 to be shown as the default option? Currently BTFS is shown. And there is no way these errors are happening this easy for me, and not across the board.
The backup time machine aspect as BTFS is what drawn me. Except now I strongly agree with @CrankyRebel to stay away from BTRFS, at least for personal out-of-the-box Desktop filesystems.
This reply within this thread helped me with this other machine. I'm back up and running well again. https://lemmy.ca/post/48538362/17944139
I'm guessing SystemD wasn't broken on this one like the other one.
Thanks @take6056@feddit.nl