After either the 3.0.13 update or a few dot updates earlier, VLC has begun to show strange combination of characters instead of the actual file name while playing the video at the top overlay. If played from MiXplorer it shows combination of characters ending with the actual .mp4 extension while played from the default Sony Album app it shows a multi-digit number.
I am on Sony Xperia XZ1 9.0 Android Pie stock ROM.