I had this problem earlier this month, needed a new spin dryer belt and pulley. I think the drum is meant to be
reasonably loose to work properly. Ask the repair man when he comes to give it a good check over. Mine is working well now, probably better than before because the belt was worn. I bought this machine in 1983 with a tumble dryer to match and they've given me good usage. I hope you resolve your problem without too much expense. Regards.