The author remixed this model.
The original is designed for M12 which is often mistaken or sold as a stand-in for PG7. This is for actual PG7 (12.5mm)
If you have issues threading into the original design this might be why (I was also confused when one of my “PG7” glands worked but then another didn't).
In the second photo you can see that one is labelled as PG7 while the other is M12, though both were sold as PG7. Only the M12 black one fit the original model. For aesthetics I didn't want to stick with the black gland.
Tip: If you are trying to pass through the Molex connector but can't and don't want to re-terminate the wires (because you don't have the equipment or are just tired of it) and don't have the fancy special de-pinning tool you can use two standard regular paper staples. Flatten them and slide them into the sides of the pins to get them out. You may have to gently sand one of them to be thinner and allow the second one to fit.