Original post by: Tim ,
Another possibility is that your drain pump is stalling. The usual design is with a rotor containing a permanent magnet. If the bearings are sticky then the rotor sometimes doesn't return correctly to the park position which means the pump stalls when it tries to run again. If your pump is like this then unscrew it (usually 3 screws), pull the rotor assembly out of the housing, clean and grease the bearings then reassemble.