How can I fix my hotpoint washer dryer wd440?

Hi my hotpoint washer/dryer model wd440 will pump water back into the machine after a wash and dry cycle. Everything seemed normal after a wash load all water out, but after 20mins after the dry cycle the drum was half full of water. Thinking that the pump was blocked we took the back off, cleared the debrey. So tried cycle again. Same problem. Any ideas how we can fix this? Kind regards, Emily Chadwick.