It was Widget Studio Plugin, but note this was my case. Did you try to access any of your config file in any place in your code?
I traced my issue by going into the engine code specificly the function that was causing this log to appear
Under ConfigCacheIni.cpp FConfigFile* FConfigCacheIni::Find(const FString& Filename)
Depending on what was displaying for you “which ini file” try to search all your cpp files