I've been trouble shooting similar problems on my PU truck. I came across a method to test for parasitic current draw by measuring voltage drop across your fuses. You need a good digital voltmeter that can measure millivolts and a chart for your fuse type and amp rating. When you get a voltage reading above 0, there's a current draw. then look up the voltage read on the chart for that specific fuse. On a UTV I'd think the draw with the key off would be pretty minimal over all. For my truck, the suggested total parasitic draw to keep the computers running with the key off is something like 50 milliamps or less, a UTV is probably less. If you find a high draw, then you've isolated the problem circuit. The technique description and charts for the fuse types can be found here... https://m.roadkillcustoms.com/how-to-perform-a-parasitic-draw-test/
Caveat, I just found this information, and haven't tested my truck. But, having an electrical engineering background, I find the theory solid.