In Settings, I had it continuously monitor my main Music folder and to add files to inbox. Once in a while, I'll fix metadata for files that are already in the library and already in the main Music folder and then get MusicBee to re-organize them. Maybe MusicBee sees those re-organized files as "new"? I don't know - most of the files that were in the inbox were no longer in their original locations.
I have a single, separate folder where I place files to be added, and add them manually from there so I never use the inbox.