When gremlins die, they leave a corpse if there is a living healer nearby/on the floor (not sure which), which may then be revived. This is a problem when a player is in a fight room, and the healer is outside the fight room - the gremlins die, and lie on the floor for about half a minute, for which time, the player just has to sit around and wait for them to expire.
Suggestions:
Lower the range (from healers) that gremlins become corpses
Don't count corpses as enemies (similar to tiny jellies - the room will open whether they have been killed or not).
A better solution would be to make all corpses disappear when there's no healer