Bosch dishwasher S10R1B?

We're having problems with our dishwasher, wondered if anyone could help?
It's not washing correctly - leaving scum and debris on plates/cups etc. We've cleaned filters, checked drainage pipes etc. I've replaced the top spray arm because it wasn't spinning freely, but hasn't had any affect. Also the washing tablet isn't being released so we've tried puttting the dishwasher tablet in the cutlery basket - but unfortunately none of this seems to solve the problem!
Any ideas from any helpful people out there? Many thanks in advance!