everyday we see on teh forum words like this:
seems to be a problem with the kdenliverc file as you run different versions of Kdenlive. Delete kdenliverc (See here https://community.kde.org/Kdenlive/Configuration) and restart Kdenlive.
maybe it's time to add on the HELP menu' the "RESET PREFERENCES" voice.
(and delete also the Kdenlive related folders? the hidden one on Linux and the 2 on Windows?)