On my ender 3 Pro I've always had trouble with pieces fitting and couldn't figure out why until recently. Two settings needed changed on my cura profile, and this test of just under an hour of printing proved it successful. Hope it saves someone else some time!

Setting in Cura is called Hole Horizontal Expansion. Needed to set mine to .5 since holes printed were all exactly 1mm smaller than supposed to be.

2nd setting is to select print thin walls.