sorry just re measured this and 123mm / 122mm - clearly needed a coffee before trying to measure. The glass from top to bottom is almost identical in both sides to.OK so it's definetly not sat square right now.
Can you measure the visible size of the glass on the left and right and top and bottom please? Trying to work out of the frames out of square through fitting OR manufacture.
You could also check if the frame is level at top and bottom of the visible glass, effectively on the beading. If ones level and the others not then the frame is made out of square. Also worth checking the top and bottom of the door frame for level. Something is clearly wrong for those two diagonals to be 4mm different..1mm maybe but 4 is unusual
Red line 123mm
Yellow line 119mm
Took a level to the top and bottom of inner bead of the fan light and both the same - running off the same way