We posted about a month ago and were having some issues with our UXV cutting out at high rpms. We took it to the shop and they replaced the drive belt and set the clearances on the valves. 2 weeks and $500 later We got it back and that seemed to help the issue with the cutting out at high Rpms. In fact our uxv used to only go 45 before the rev limiter kicked in but now it goes 51 mph. Only issues is.. now the uxv stalls and or won’t start at all. It isn’t from it being hot, as it can happen after it’s been sitting for an hour an a half. Tonight I drove it hard for about 30 minutes no issues at all. Let it sit an hour and a half and it wouldn’t start (see video). It acted like it wanted to start but it didn’t. We Let it sit another hour and it fired right up. Other times we will be driving it and it will just start puttering and then die. We usually have to let it sit for some time before it will restart. It is beyond frustrating. We took it back to the shop and they said they drove it 5-7 times a half hour at a time (I call bs on that) and it never did anything we described. We have never had this issue before until we got it back after the last work on the belt, etc. any thoughts? We are getting ready to go hunting and set trail cams and don’t won’t to be stranded. I attached a video, please excuse the frustration. 
The shops are not the place to take an intermittent problem. You don't have enough money and they are not allowed to take the time which will be enormous. Seemingly non-repeatable, inconsistent problems demand logical elimination of possible causes. Spark has been mentioned so let's start there: do you get good spark EVERY time you start the sequence? Rig a test to find out. Last year it seems I had an intermittent fail to start with a code indicating a bad injector. Resistance check of injector showed in range. Found a bad relay. All is well once relay replaced. Later, had a fail to start or it quit running. Now what, I asked. Found the injector plugged with the slime caused by ethanol fuel! Huh? This machine was new, old stock. From 2013. This problem was 2019 and after several thousand miles of trouble free riding. Some of that "dealer gas" was inthere three years before I bought the machine!
So you are going to have to either test each system to find the cause or try to sell the machine.
