Are you using A3 paper or US Letter A3 size? One is longer, but thinner than the other which might account for the problem.
A3 size is 297mm x 420mm, US Letter A3 is 11" x 17"
It's Trupix double letter A3 size that I'm using, can't find a measuring tape to get exact measurements from it.
Going to have afooter about with it and see if I can get it to work.
I just adjusted the paper tray to A3 size and the paper fits, but the lid won't go back on, don't know where I've went wrong, hopefully with a fresh head this morning I will figure it out.
When I put the A3 as landscape, and place 2 sheets of A4 on top in portrait, the A4 overhangs the A3 at the bottom, and I have about half an inch showing on the left hand side of the A3 landscape.