Just came across this thread ...
I have a 2020 Hisun Sector 750 (bought new in Jan. 2021). I must be one of the lucky Hisun owners given I've had only a few minor problems. I haven't experienced any starting issues and my UTV sits idle from mid-Oct. to mid-Apr. with a full tank of gas, and not hooked up to a battery maintainer. However, I only use premium fuel and always add fuel stabilizer to every tankful.
I do this also for all my small engines - chainsaws, lawnmower, lawn tractor, log splitter, etc based on the advice of an oldtimer years ago. Haven't had a fuel-related issue in years.