Help needed please. My husband kept tipping his dining chair backwards. Our son suggested an office chair, which was fine but he was too mobile. I tried to get lockable casters for it, but the chair has clip in casters and the lockable ones seemed to be all the screw in type. When I got his new wheelchair I thought I had solved it by wheeling him to the table and putting the brakes on, but after 3 days he has started tipping the wheelchair onto the back two wheels. Has anybody else had this problem please? Is there a solution?