Hi and welcome here!   Ok, there are several things you could check:  Where do you measure your cube? Because don't measure the vertical corners, they could be bulged out and your measurement is wrong. Print slow, about 25-30 mm/sec and set all speeds (there should be 6) all to the same speed. Turn off acceleration and jerk control in Cura Uncheck infill before walls Check setting "Slicing tolerance" and try inclusive/exclusive settings instead of mid