I've been looking over the Staghound to try and figure out why it's broken and i think I know what it is.
As you see here, look at the arrow, it's in the
requirement table, which means that this upgrade is required for Vet 2 I think, so because the Staghound doesn't have the slot item "commonweath_stuart_canister" it doesn't get that upgrade.
Also if you look right under "action_02" it says "Validate all subactions = true" and also "check self = true"
This is why Staghounds can't vet up past vet 1, it's because the Stuart vet was copied right to the staghound along with the additional shot, which even needed.