If you shift it while the drive train is rotating you are damaging transmission parts like the fork(s), gear dogs and gear teeth. DO NOT ever shift it while moving. Now...it's hard to shift because power or force is being applied to the belt while it's supposed to be disengaged from sheaves. This can happen if the idle is too high, which means a problem with the IACV, throttle cable or throttle e-module. In units with a wet clutch is can mean a spring has come loose from one of the shoes or a bearing on the half-shaft is failing. On units with no wet clutch, and ones that have had water or mud intrusion, can mean the idler bearing is seizing up. In 2022 there were both wet clutch 800s and dry clutch 800s. I suspect yours may be the dry type. If there is a retainer bolt in the center shaft and a larger nut outside of that, it's a dry clutch and I would be looking at the bearing the belt rides on at idle. All of them fail quickly.