Resident Evil 4 Stuck! Serpent Ornament (castle!)

[southpole87]

Once i saved ashley from being trapped in the bars, i never got control of her, i stayed as leon, cleared out a room then got back with ashley. and it wont let me back into the room!
i went to a guide and it says that the serpent oranament is retrieved by ashley when you play as her

 

[Devinelogic]

When you completed the sliding block puzzle which unlocks the door, go through and there is a chest with the dais inside which lets you get out. When you take the dais, the chest should turn to reveal another chest, inside should be the serpent ornament, and then the knights come for you so make a hasty escape.