Hello, due to the size of the uPrint SE Plus printer, I divided a large rectangular-like object into four pieces. To fix the pieces serially on a metal plate, I use screw holes. After all four pieces were printed, I tried to combine them into one big piece. 3 pieces are already fixed to the metal plate using screws. When I put in a middle piece, I found gaps. What could be the causes? How can I fix this problem? Any suggestions appreciated. Thanks.