Could be a couple of things, if in angle mode it can be trying to correct to get level by pushing one motor harder 3 and keeping the other motor throttle low on motor 1. If the motors are across from each other on the frame (diagonal) then it may 'think' it is tipped diagonally. When you do a pitch forward the back to motors should go up in speed and the front two motors should come down in speed, if you pitch back the front two should spin up faster and back two should slow down, roll left the right two should give more power and left two should sink, roll right the left two should go higher and right two should go down. If you aren't seeing those patterns then best guess is something flipped. The 1 and 3 being off thing could just be it trying to correct from bad accelerometer calibration or just from vibrations on the table if in angle mode, usually in air/acro mode it won't have that kind of angle correction going on but it might still spin all the motors up and down 'randomly' since it is trying to hold current angle still instead of trying to get itself to level. Hope it helps, sounds like you're very close.