if you have a HQ chair that gives you 30% stamina a tick, and you have 80% stamina remaining. the chair will not heal your stamina anymore. i am guessing it doesn't want to go over 100% so it just doesn't give you any stamina at all. The better the chair, the more annoying this gets.
this has been bugging me for a very long time but i couldn't find any previous posts about it.