how can I fix hoover tumble dryer?

I just open up my hoover tumble dryer to replace the capacitor then put everything back together and works fine apart from the air is losing out from the dryer door, and notice the air vent is not blowing out strong enough due to the air has past through the door and fill the room with full of dust.! if you put your hand around the door you will feel the air past through I try everything but has no ideal what cause it, can you help to fix problem please?? manu thanx