I’ve found that my printer STEPS per mm were non correct and prints came out slightly bigger than it should be (the calibration cube came out 20.20×20.18, instead of 20.00×20.00)
2 days of calibration and a lots of cubes later, I managed to get a quasi perfect cube of 20.02×20.03mm.
reprinted 2 pieces and works perfectly. Tight fit. Someway too much indeed…
Recalibrate the Steps per mm and it will be good.