What color is your oil?
If you can't see an air bubble at the top of the sight glass, it's too full. Too full means aerated oil and that can cause a sticky shifter, as will gasoline or water in the oil, more so when hot.
But I've not seen a PNF fail to work. Huge job to disable, a case split.
When i changed the oil last, i put in only 3qts (which i thought wasn't enough) and it was halfway through the sight glass. when i ran it the first time, the oil level would drop, and then when parked on the center stand would reach the halfway mark on the sight glass. after continued running, the sight glass would be too cloudy to see anything.
anytime i drained the oil i never saw any indication of gas in it, and i'm familiar with what water/oil looks like, so i don't suspect that either.
It would shift ok for awhile, but then it was overly stupid. I figured 3qts of oil wasn't enough, so i put probably 1/2 a pint in, and things got a bit better, but still can't see anything through the sight glass.
shifting tends to suck the most when everything is cold, but gets better when warmed up. i know i'm burning a bit of oil in the rear cylinder (exhaust valve seal). It's frustrating that i can't read the oil level to see if low oil is my problem, but anytime i changed the oil it would run great for awhile. It's always black as death when i drain it though, but no chunks or anything solid in the screen.