Scrolling through media sources list with multiple CIFS sources freezes constantly

Since I cannot rescan just a part of my (overly large) CIFS volume, I have added one media source per subdirectory (series), thus ending up with 50+ sources in my media list, all of which are CIFS.

When scrolling through that list to tell one single source to rescan, the scrolling stutters and freezes almost non-stop; we're talking about 10+ second freezes every 3-10 items scrolled. During such a freeze nothing responds. It can take up to a minute to reach the last media source in the list. I have a hunch that merely scrolling through the media list does some interaction with the actual mount.