So this happened to me too. Calibration cubes and other stuff I’ve printed has come right right on the money and I have some mpcnc parts that are too small. I use cura and I wonder if that is a factor. Filament is Foxsmart 1.75mm pla clear. Machine is Hictop Prusa i3.
So I printed the 2 corner blocks at .2 layer height then in a effort to cut down print time I lowered the other two and the rest of my parts to .3 layer height and left all the other settings the same.
The ones printed at .3 are almost perfect for the US 3/4 conduit. They fit super snug but fit. The feet are the same deal printed at .3 they fit.
The .2 roller blocks I needed to take a good amount of material out to fit the conduit. Now with the .3 Flex foot on the .2 roller block I can see the roller block is a little over 2mm less wide than the flex foot. The .3 corner block is exactly the same size as the flex foot.
My Corner Block locks printed at .2 layer height are the correct size.
All my rollers are tight but if I slide them back and forth slowly it look enough of the galvanized coating off for them to slide smooth. There is two types of conduit a thick walled one and a thin walled one. I have the thin walled one.
I find the whole thing crazy and shouldn’t have happened. I blame it on some crazy cura bug on not on the design or my printer. Changing the layer height should not change the scale and if It did then my corner block locks would be off.