Digitrax is not announcing the "latchign F2" problem because it is a bug, not a feature. They don't want the world to know they stuff is buggy. I've been doing DCC for quite some time, but this is the first time I have heard of that problem. However I really dislike Digitrax DCC (both their hardware and crappy manuals), so I try to stay away from it. But since it is the most popular (and most feature-rich) DCC system in North America , I often have to hold my nose and use it. For example some friends use it on their layouts, and my NTRAK club also uses Digitrax. Still, every time I use the system I cringe! I do have to admit however that their latest versions of throttles are finally designed not to be more ergonomic and intuitive, and they no longer look like cheap pocket calculators from the '70s.
Anyways, I'm glad your F2/whistle problem is explained. What I don't understand is why the problem also showed up when you used SPROG? That doesn't use a Digitrax throttle, doesn't it? I specifically asked you to try the F2 button using SPROG. That would have speeded up troubleshooting.
Ad to reiterate what we have been telling you all along: decoders have no concept of (or ability to set) latching or non-latching functions. It is, and always has been done in the DCC system (throttle/command station). This fact is very clear when you understand how DCC works.