Have a look at /storage/.kodi/temp/kodi.log for errors/issues. My thoughts would be a corrupted DB file or something add-on related. Worst case stop Kodi and rename /storage/.kodi to /storage/.kodi-old and restart; then start copying back config/content items from the old install until you either find the problem or end up with a working install again.
How do I look at that? I'm having the exact issue.