VLC IOS 3.03 German: WLAN share rejects certain videos

[Caup]

I'm trying to copy video files to IOS devices, but failed for certain AVI files.
All files are part of my NAS video collection, all verified by TV, PC and IOS usage via network share.

I tried transfers via WLAN share by drag/drop into the "Datei hinzufügen" window as well as by "+" file selection.
Both times, rejected videos are transferred to IOS device, but never show up within media library.
(Successful transfers are typically acknowledged by name within the drop window, which is eventually replaced by a "100%" message, before those videos show up within media library.)

As I experienced so far, file size might be a problem.
All successful transfers were < 2 GB, all rejected > 4 GB.
Unfortunately, there were no error messages given.

Any hints where to look for a solution?
Thanks.
Peter