Engine overheating

Has anyone had a overheating issue like mine? I’m at 760 miles and 68 hours. Today we were on the trails and everything was going awesome. About 15 miles in we pulled over to give the boys throttle thumb a break. I always keep the engine temp on the gauge. When I shut the machine off I was at 201. Normal. About a minute or two later we hear a pissing sound and sure enough its my machine. Took the hood off and its pissing out the little hole in the overflow bottle. I turned the key on to see the engine temp and its at 230 and going up. Odd to why temps go up when the engine isn’t running. It peaked at 238 and slowing went back down. So I’m wondering if my radiator cap is malfunctioning. We drove another 5 miles and pulled over to test this theory. I shut the engine off at 200 and sat there for a minute and turned the key back on. It was at 220. I started the engine and the temp immediately drops to normal. My cooling system is full, radiator is not clogged, cooling fan is turning on and off when its supposed to, cooling system is still on the factory fill and never been opened until now when I topped it off. So I doubt its an air pocket.