CL360 shifting issues

Hello, I am asking for help to troubleshoot an issue with shifting my 1975 CL360 with 6-speed transmission. It runs great and most of the time will upshift without issue. When accelerating in the upper rpm range, the shifter will not always engage the next higher gear. It will find a neutral state between gears and require another effort at the foot lever to pull up into the higher gear. When I shift at lower speeds I can shift without using the clutch.

I removed the side cover and clutch today to check the movement of the shifter arm. The printed manuals describe adjustment of the "overshift travel" (Clymer #M323 250&360 twins 1974-77 on page 25) but I cannot find mention of how this travel is adjusted.

Here is a small video of the shifter detent mechanism in play during shift while the rear wheel (output shaft) is moving. The clicking noise is due to the kickstarter gear not fully retracted.

What are your thoughts about possible causes for the incomplete shifting? I had the bottom end open in 2018 to inspect the transmission gearing, and found no visible wear on the gears, dogs, or shifting arms.