We’ve been having trouble since delivery with stiff operation of the door handles. I’ve now learnt from CD that the door mechanisms are not lubricated in the factory, primarily to avoid dust sticking to the lubricant during the manufacturing process. However proper operation does require lubrication.
I’ve found the latch pins themselves benefit from a little Dri-Lube, which is a hard grease-like substance that comes in a stick form. The interior mechanism also needs lubrication, and this will be done on our plane next week when it has a 100 hourly inspection (total time now > 350 hours).
There is also apparently a procedure in the maintenance manual for adjusting and checking the position of the latch pins which if done properly will ensure that pulling the door to will cause the pins to snick into the plastic sockets on the door frame, which then makes operating the handle to lock easy.
To quote Walt, “Don’t slam the door!!”.