How is VLC connected to the speakers.
It sounds like an impedence problem in that those are the most common.
Always better to turn up the volume via the direct control for them other than increasing the signal directly from the source.
I have resolved the same problem, in my case it got progresivly worse. Until I had to look at other media players, all of which just dont cut the mustered. at first I thought it was VLC 10.3 so I erased - re installed, without success, then I erased it again and fished around for 8.6 still no joy. F...