Having an issue with X that persists when reverting to previous generation

I recently attempted to switch to stumpwm from kde. When I tried to run startx, I got an error message (which I did not record). I rebooted into the previous nix generation, and was surprised to see that after logging in the x server froze. I still had access to tty 1-6, and everything else seemed normal. I have tried various changes to my configuration.nix, but the issue persisted. Is there some way to completely reinstall X?

Nixos version: 18.09.2096.2ff7ef373e5 (Jellyfish)
though when I installed stumpwm I was running unstable, as I had thought the stumpwm package was only working on unstable.

Update: I have tried to follow the instructions here to get more information:
But when trying to start x I get the error “Cannot open log file “nix/store/rapmyalv96saywzxc1n59mnd9c62jz08-xorg-server-1.19.6/var/log/Xorg.0.log”