Bought two of these (2 ups) last fall. Newbie. Started using them in the spring. Only about 300 km on each. One shifts quite well. The other is getting more difficult each ride. Shifting from any gear to any gear is difficult, all the time. Is there a reasonably straightforward fix or is the (very faraway) dealer the only answer. I expect the warranty will cover this.

Its common on them... At me it starts to shifr light in about 1200km

Very easy fix, you can adjust the foot brake safety release right at the foot brake (just take the panel behind the RF wheel off and it's right there, I screwed mine all the way out so I don't have to hit the brake to select a gear.) And if your actually shifter isn't lining up with the notches (for park, reverse, neutral etc) you can pull the left kick panel off and adjust the shifter rod length (the rod between the shifter and the trans) to get it perfectly lined up. Mines shifted like butter ever since I adjusted these, before I could barely shift it at all.

Thats the truth, but he asked between gears, not reverse and park. Shifting between gears has nothing to do with foot brake

you can adjust the gear rod on the right side of the atv if you remove hi right side panel.  worked on my 520