Help me clear up this Roon mystery

From time to time I find Roon adding and identifying music when I’ve not recently added music or initiated a scan. Can someone explain why this happens?

Is your music on a NAS? Maybe your NAS is re-indexing files which make Roon thinks the files are new/modified?

Yes. A QNAP. That does something or other every day at 3 AM but otherwise is pretty quiet.

I do not know the QNAP. I have a Synology myself. On my Synology, as soon as I install a Multimedia package, file-indexing is also switched on which runs in the background. This ‘touches’ all my music and video files. If such thing happens on a QNAP I cannot tell you.