I found a post that seems to list a similar problem but it is older and solution seems unclear except trying to replace light dm with gdm which may not be a solution.
Another thing that you could try at least is login in lts kernel. if not yet installed, sudo pacman -Syu linux-lts linux-lts-headers then reboot and select lts. That is a wild guess until someone more knowledgeable pops in to look at your config files. However, it never hurts to have a backup kernel in case something goes sides ways with driver updates.
I don’t know current problems with bspwm since I don’t use it… Hope you will find a solution.