I had the same thing happen to two different sleds a couple weeks ago. We were at 12,000 ft and it was warm. My 2016 Arctic Cat m8000 would not start after taking a break. I tried taking the cap off and it didn't really make a difference. We had to pull the cord for about 40 min. While all this was happening we looked and gas was pouring from the left front of my 2017 summit 850. It dumped a lot of fuel. We let it sit, and tried to take off the gas cap. It was a geyser, i had it practically lift my hand in the air. I had to quickly screw it back on. I had to crack the cap till it leaked for about 30 minutes. We finally moved it off the pool of gas and it started and ran fine. The M8000 finally started as well, but it took tons of pulls, the skidoo had e-start. It was really warm and high altitude. We went to a lower altitude and bothh sleds were normal. We had two other arctic cats that ran fine and never had a problem.
Just a note, both sleds were facing downhill as PaulAnd mentioned earlier.