Vacuum pot/actuator/canister for HVAC doors

I've broken two blend door cables in the past and in both cases found the foam on it had deteriorated and in the heat of summer the adhesive glued the doors shut.
Could be that the canister is OK, but something is causing the door to not want to move.
Usually, not always, those canisters just 'pop' and fail to work. Easy test is with a hand pump to see if it holds position. If it retracts, then slowly moves back - it's got a leak and is bad. If it doesn't, then something else might be causing drag. If the door isn't returning to rest, the spring inside the can could be worn and a 'helper' spring might work, or again there's just drag on the door from debris or rust on the pivot shaft. I'd try squirting a drop of motor oil onto the blend door shaft to see if it helps - assuming it can be reached.