Found the problem. it was the plugin nodebb-plugin-merge-subtopics
It could load any category page with sub-categories in it.
Maybe it's hepfull for somebody who has same problem 🙂
I deleted nodeBB folder and cloned the latest version for a fresh installation. when I was installing nodeBB, it recognize the old database and used it!
What is the right way to remove nodeBB fully: database, files, etc?
You need to clear the database you are using, for redis you could use the
flushdb command and for mongodb I believe it
If you used Redis in the first install, deleting the DB file in /var/lib/redis should do the trick.
@planner Important to note that if Redis is running, then the
.rdb file is a disk-persisted backup, so even if deleted, if the redis server is running, it will eventually save back the same database data into the .rdb file.
Good to know.