So, I messed up with moodledata directory - I moved it to another location and entered info in config file.
After that, I constantly get error
Request for an unknown renderer core, files, general
whenever I try to add something (after getting "add activity/resource" window) or post in forum.
It is so similar to this one: https://tracker.moodle.org/browse/MDL-40136
I am pretty sure it is trivial, but workaround by deleting cache is not working
Also, I should mention I added a "File system" repository, but I deleted it: I guess it does not affect this issue.