Washing Machine Keeps Sticking On The Wash Cycle

Hi

My Bosch Exxcel 1600 washing machine keeps sticking on the wash cycle. The timer will count down to 1 minute but it's still washing and not moving to the rinse cycle. The first wash of the day always seems fine but it goes wrong with the second. I've just done a load with a prewash and the prewash was OK but it got stuck at the normal wash.

The only thing I can do after this is to put it on the spin cycle to empty it and drain the clothes a bit and then do the rinse/freshen up cycle to rinse then spin. All of this works fine.

I've checked the filter at the front (by draining with the little pipe, removing the cap and checking there's nothing in there and that the wheel turns).

I've checked, by touching the glass in the door, the water is heating and it feels warm.

Do you have any suggestions as to what to check next please, before I need to call someone out? My husband is quite good at repairing stuff but I don't want to ask him to pull the thing apart until we know what we're looking for.

Thanks

Karen