Sometimes when in multiplayer session i could encounter a bug when rounds being fired with M203 Launcher floats in place where barrel_muzzle (bone where projectile is spawning).
It's happening most likely when i im firing round after round, while having more than 30 rounds stored in vest or backpack.
I can't reproduce that bug in local GameMaster scenario, it only being spotted while multiplayer and what is more mostly it was happening when servers were full.
Most of players using my Mk19 mod were able to reproduce this bug by simply shooting whole box of mk19 rounds.