OSMC rescans library for unknown reasons (hash problem?)

Every two or three months the PI wants to rescan all movies from my media devices, which are included via network/SMB. I have no idea, why. There seems no logical reason. I already had this with Raspbmc ‘years’ ago and now with (a fresh installation and on a different SD) of OSMC, so it has probably nothing to do with OSMC in particular. I checked the MyVideosXX.db with SQLite and could see, that all paths to the movies are correct. When I have to rescan, there is a new entry for the folder with a new idPath (of course) and the only difference to the old “path”-entry is the strHash. Could this be the problem? How can avoid that? And why the Hash has changed? The media devices have always the same root/path and same IP. Could the fritz/avm-router be a “problem”?