Small update on this bug, might be intended behavior, if combat has started somehow but the player hasn't been noticed and isn't being targeted yet by anyone (no In-Combat buff on the player) or maybe if you managed to silently kill the only enemy that noticed you out of the group but combat is continuing because there is some kind of in-fighting going on that doesn't involve you, then you might be considered out of combat and able to perform actions like recharge shields.
