I tried it, and I cannot replicate the problem. Both with a default airplane, and with the FS Labs A319-X, latest version 400.
The thing I noticed in your video, is that after you select Boarding, the jetway moves immediately, when instead you are supposed to see another menu that select which door you want to dock to. Is it possible the FS Labs plane is controlling the jetway too as part of the GSX integration ?
Does the jetway work if you just select "Operate Jetways" ?