Edit: this is for the silver PSU only!
The Original Design's supplied STL files for the socket had a wrongly placed top socket holes, as found by me and multiple other commenters.
UPDATE 12/5/2021: Original design seems to have disappeared off thingiverse, I think its new home is at prusaprinters: https://www.prusaprinters.org/prints/993-prusa-i3-mk3-psu-cover-with-rear-power-input
I took a look at the .STEP file and the socket hole was in the right place, so I suspect something happened in the original STL export process from STEP to STL.
So what I did was I took the .STEP file and re-exported (in high quality) from Fusion 360. I did not make any changes at all to the design. The STEP files contains the socket w/o Wire gap only in case you were wondering why there's only one version here.
Category: 3D Printer Parts
The author marked this model as their own original creation. Imported from Thingiverse.