Some MP3 songs seem to disappear from PA (not from phone)

[Roller]

When I do a (re)scan of my music files the count of all titles are shown correctly. Folder cover (art work) is also displayed. Count of titles in each folder is OK, likewise count of all titles. But when opening some folders there are no music files inside. Instead an error messages is displayed:

  Doesn't look like anything to me.

Strange message, no music titles available inside - but embedded cover and count of music titles are shown (see screenshots).

My MP3 music collection is really huge. Is there a limit of maximum files?
PA version 2 has never had such problems and works since more than 5 years with different phones (Huawei, Samsung, Xiaomi). The problem has begun after update to PA v3. Neither data reset nor full rescan does help.

Phone is Xiaomi Redmi 5+, Android 7.2, 64 GB internal memory and 256 GB SDcard.