Hymer cupboard shelf problem

[George Saltash]

Hi everyone, I have a Hymer swing with a roller door cupboard at the back near the entrance door. Unfortunately I put a back cover on the top shelf to stop items jamming the roller door and that cover is now jamming the roller door!! I am trying to remove shelves in the cupboard from below and have removed the four fixing screws from the underside of the bottom shelf, but the shelf is still completely solid. Does anyone have any experience of removing these shelves as I cannot see how they are fixed now I have removed the bottom brackets?!?!