One y axis front and back attaching plates not level

As I’m assembling my MK2 30x30, I’ve noticed both of the y axis rail attaching plates are about 3/16 gap instead of being flat on one of rails. The other y axis rail is flat on the table. I’ve loosed up the front and back screws, but no change.

possibly the holes in the rail on one side are not drilled perfectly alligned on the rail? possible rail is slightly twisted? I’d check both sides!