not sure if bug or intended

uk based xbox series s and x

Faridun infantry with shields on the dreadnought.

they seem to take damage at bizzare intervals.stun bar fulls up randomly in chunks instead of with damage.
random times they take no damage until after they recover from being stunned

only come across this so far with crossbows. specifically rapid shot and armour piercing rounds. I'm shooting 2 magazines full to get zero damage or half enemy life.

only time I don't come across this is when I have pierce support enquired to the skill

it is making progress through the dreadnought take a overly extended amount of time