I have printed this part and checked the location of all 4 screw holes and it can be mounted in 90, 180 and so on. If you are off by 2MM it might be you setting out your printer out of calibration. Try downloading the 20mm double its size to 40MM and print with low infill and see if it is 40MM in all directions. The larger you print it the more accurate of a reading you can get. Sorry to hear that you are having issues and I hope that this will help.