Notice how your hits started registering only once you moved a bit to the side, as if something invisible was blocking your shots server-side, but not client-side since there is blood coming off the enemy.
Turns out that when the windshield on the kubelwagen is lowered, its collision doesn't update on the server, causing clear hits to be rejected: https://www.youtube.com/watch?v=uP5cyvtUlYE
Paging /u/DRUNKKZ3 /u/lytlb1t
Yeah looks like the kubelwagen is blocking it, great investigation! I'll check tomorrow whether the issue was already reported and if a fix is in progress.