I dunno... It sounds like an odd problem. I can't see how the thing could get out of time unless one of the roll pins in the hook drive is half broken. Mabey some disassembly will flush that out.
I also have a little green ba$tard (327) and it was doing something similar to the knot you pictured... on occasion. The rest of the time it was tieing the upper and dropping the lower. I sharpened the twine knives. I played with the finger and holder tension... adjusted the tucker fingers... all to little or no effect. When I got looking at it while it was running I notice that the upper hay dogs were not falling sometimes and when they didn't fall on a tie cycle... it missed. The short story is that the wrist pin on the plunger had nearly fallen out. The symptoms began something like you're dealing with and grew worse until it wouldn't tie a damn thing. New pin and bushing and it works like a charm.