Inserting Hex Nuts: To ensure that hex nuts are properly seated, do the following:

Add a washer to the screw, to avoid damaging the printed part.

Insert the screw through the hole on the opposite side to the hexagonal cavity.

Thread the hex nut onto the screw and tighten the screw.

Ensure the hex nut is aligned with the hex cavity while tightening.

When the nut is fully seated, remove the screw being careful not to dislodge the nut.

Inserting Nyloc Nuts: You can use the same method as used for the hex nuts.

Inserting Square Nuts: They tend to fall out if the piece holding them is inverted. After they are inserted, check that they are properly seated by inserting a screw to engage that nut.