It seems to be only affecting in these months that QFile Pro (or recent update of QNAP) has implemented a file name length limitation on top of the ordinary limitation from ext4.
Now 50 ASCII characters are the length limit of a file name (including suffix), according to my testing, no matter where the file goes to (even if you upload it at the top of possible directory). I would like to ask if this should be normal.
If so, I would wish that this limitation to be removed (since long name is common, and 50 characters are not lengthy at all). This really hinders backing up files from phone (since apps tends to concatenate names, which lengthen the filename).