Possible blocked filter?

Hotpoint Aquarius WDF740......motor failed to start to drive drum....program 5 stuck at 0:01...fiddling about I eventually managed to get it to zero and empty the machine. Electric off, water off, waste pipe secured and machine pulled out to gain access to the rear inspection panel....5 self tapping screws removed...everything looking good...gave the pulley a spin to see if it was seized..all ok. So , thought I, lets give it a go. I set it to the 'B' function to spin and it started ok ran until the program finished. Then the program reset to run again and this time there was no drive again to the drum. Still in this state..I've checked the filter at the front of the machine which was clear but I believe from reading issues that there is another one? Please advise.