Shifter Question

I know I am a worry wart. I have a 2015 RZR570 with 340 miles. The shifter handle takes a lot of force to make it move. My wife is small and she can barely move it. Even when the buggy was new the handle was hard to shift but now getting worse. I have changed out the trans fluid several times since it was new. Is this a normal condition? Also for example I may shift to low. The gage would say "L" but the buggy would not move I would have to put it in low again. The same for the other positions. Does the cable need adjusted?
Is there a maintenance time that I am to bring the buggy in for a check up under warranty? I did not see it in my paper work.