I have the same problem coming up when I press some key on my keyboard while being in the garage. But that's the only problem I have with the hud. And if I reboot the game and load my save again the problem is gone.
Yes. And I figured it out now -- this time for realz. The problem has nothing to do with savegames, but occurs *only* when you press a 'sandbox' command (in garage/at helipad) while the 'store this vehicle in your garage' message is still being displayed! (It takes a while to dissipate). In that case, the new sandbox command message won't get displayed (as there's still another one up?); and the old one (the 'store this vehicle in your garage' message) isn't closed any more, either (presumeably, because the sandbox mod tries to close the new instance of its own message, which wasn't displayed to begin with. Resulting in the old 'store this vehicle in your garage' message simply never being closed again).
I tested this extensively now. And, indeed, it seems to be what's happening. The solution? Obviously, on my end, to be a bit more patient. I can imagine other occassions where another status message is already being displayed, though. So, if there would be a way for the mod to either wait for existing status message to have dissipated (if one can even test for that), or have it close existing ones first, that would solve it.