can't refit condenser unit into hotpoint aquarius tumble dryer?

I am having trouble fitting the condenser unit back into my dryer - it won't fit back in snug / flush and so the door won't close properly. Took it out to clean - as the manual says - and have put it back in the right way - but it just won't fit back in like it was! Can't see anything stopping it - has anyone else encountered this?? Is there a trick to it - help!!
anna nov 09