So installing the seat the way the video shows or how I've always done it before on multiple kayaks, results in the seat almost never locking in. Using your suggestion I did find a technique that is somewhat successful. If I place my front hand around the seat frame and seat adjuster bar, where the side of my thumb/hand runs along the top of the seat frame and four fingers spread out along the bottom of the seat adjuster bar, and squeeze tightly right when it 'clicks' into place while rotating back, it sometimes works.
If used in this manner continually, my other concern is the area where the rear starboard corner of the seat frame contacts the hull. I don't believe that contact was normal before this issue arose. It's hard to be sure though as before this I never paid much attention to any of that as the seat just installed easily. The seat in my only other Hobie right now doesn't do that, but it's a Vantage CTW so that's different.
The mystery to me is what caused this seat behavior to start at a specific time. It was never an issue until after a certain outing, now the locking on of the seat definitely behaves differently. The seat was only a month or two old (used maybe 10 times) before this started. (It was a warranty replacement after the recline adjustment quit working on the original.)
https://photos.app.goo.gl/RMDUjd8T4xCrnD5g7https://photos.app.goo.gl/sYxVM5RU6vv6Zgo2Ahttps://photos.app.goo.gl/yvzTunfXKqNF18Tu9