He sent me a private message saying that holding the power button down solved the problem.
Letting the player intentionally discharge while it is stuck in place might not be a good idea, as the battery gauge might not be functioning properly then, and running the battery too low might damage it. If a player is new, it would be a good idea to run the battery down to around 20% or so for one or two charge cycles before charging it. The battery indicator might not be properly calibrated on a new player though, but running the battery down(not too far though) will help make the battery indicator more accurate. Initially the player might turn itself off before reaching the 20% mark indicated by the battery meter.