I installed a theme on CyanogenMod 13 that is incompatible. Now my System UI keeps crashing.
I can't find it with the file manager. How can I delete the theme?
Is there any way I could fix this without reinstalling or factory resetting?
Although I'm still on CM12.1, I can relate to you.
Reboot to Safe Mode. Go to Settings > Apps > (Your Theme). Uninstall it.
Hope this answers your question.