I was afraid someone would have trouble with this.
I despise the design of both the radiator drain plug and the cooling system bleeder valve, located on the same side of the radiator at the top. They appear to be designed somewhat like a Dzus fastener, where a plug has a path carved into the shaft that a pin of some kind follows.
https://www.aircraftspruce.ca/catalog/h ... teners.phphttps://www.baysideperformance.ca/woodc ... stener-kitIf you are ham-fisted with the drain plug or the bleeder valve, you can really bugger them up because of this design and the fact that the radiator and the plugs are made of plastic.
The trick with either the drain plug or the bleeder valve is to GENTLY break them loose with a properly fitting wrench by wriggling them back an forth a little... this helps to get the o-ring seals inside un-stuck so the plug can actually move. Once broken loose, the pin will follow the path carved in the plug, (there may exist a reversed design where the pin is in the plug and the path is carved in the side of the hole), and the plug will pull itself up and out of the hole, allowing the fluid to flow or trapped air to escape as the case may be.
Dzus fasteners are excellent for aircraft body parts and similar applications, but for this application seems like the manufacturer is re-inventing the wheel to create unnecessary hassle for the owner so he or she has something else to take into the stealership to work on.

If you happen to break a drain plug or a bleeder valve, it may result in having to replace the radiator.
It may be worthwhile to see if there is enough material surrounding the drain plug to drill out the entire darn thing and install a proper brass drain plug or drain petcock.