This obviously means that an upgraded package is causing the issue.
Correct me if I’m wrong, but these logs appear to be for the boot subsequent to the crash? Only the journal logs around the time the system starts to become unresponsive can be helpful.
Regardless, if the system works fine after a clean install but starts failing after a period of usage, the logical conclusion here is that some update broke the system. Therefore, your next course of action would be to check your pacman logs to identify the problematic update. Check the timestamps in the pacman log that correspond to the time just before the problem started to occur. Once you’ve identified the suspected packages, downgrade them and see if the problem goes away.
Here’s a friendly reminder: Do not do this.
If your system hangs, the first thing you can do is to try to switch to a TTY. If you can switch to a TTY, you then have access to the journal logs, which will help you diagnose the problem. If all else fails, the sysreq key and REISUB is your friend. If you want to know how to set this up, there is an excellent guide written by our friendly neighbourhood Frogman on this very topic.