The stairs were 100% serviceable.
The door wasn't opened until the stairs were in place, although the 717 is not operated by QF so their policy has little relevance to what the CC did, however QF policy certainly would be reflected in COBHAM policy.
QF policy should have been followd by groundstaff. The stairs were removed whilst the door was still open, it really is quite simple. It was a mistake.
The CC is OK considering. More tests to determine the longer term outcome.