When the boom truck is used, there are phantom collisions from what I assume to be hitboxes from the boom. Unfortunately I can't really provide any more information that this video:

I think it has something do do with the applyAfter since it does not happen when the boom is stowed (no animations), and in the past there were related hitbox problems (#1031)

If you re-load the world, does the boom end up in the spot where the phantom hitboxes are? I saw some oddities with variables not updating in the past. Wonder if that's what this is.

I haven't really been able to recreate the issue, but I think that when I reloaded the world the phantom hitboxes disappeared (or re-synced with the boom). I don't remember the boom model moving unexpectedly.

Closing then since cannot reproduce.