Stuck on the story quest due to a potential bug

Hello, I’m trying to level a testing character, but can’t get past the early Hallowfall quest
[A Lamplighter’s Duty] - where we have to board a tiny flying boat and hit shadow attackers with the beam of light.

The beam just goes through the mobs and doesn’t hit them, won’t focus on them to land a hit, but always stays directed somewhere beyond visible distance.

Can’t figure out if it’s a bug or am I doing something wrong, but had no issue with this quest back on the 11.0.5 PTR. Relog, restart, disable addons, scan and repair - nothing helps. Any workaround for this? I reported it as a bug a while ago, but I’m guessing not many have the same issue, so maybe it’s a problem on my end somehow.