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The only thing that sticks out to me is you both seem to be printing at pretty low layer heights and you both seem to have a problem. Mine was printed at .2mm layers height. While I do remember having to bore out the PCB mounting holes, I had no problems biting the screws into the plastic to secure the two halves together.

Are you possibly under extruding? Maybe find a calibration print on Thingiverse and test fit 3mm bolts into it to see if the calibration is off?