I had 2 of these PV's and both did the exact same thing. I tried to use contact cleaner spray for electrical switches and it helped some. Still have some sticking. I figure its the nature of that switch after a month or two of use.
If you are out of warranty you can send it back for a rebuild for I cant remember how much it is. Something like 35.00.
If you are in warranty they should fix it for free.. Put in a new switch.
I dont know if they use a different switch now or not but many of these had the same problem. Nice
mod outside of that one annoying detail.