I've had similar weirdness with the Mtronics ESCs. My SWM Trenchant came with a Marine Viper 15 in it. With a SubTech Subsafe, blow actuation is immediate upon loss of signal, along with chattering of the control surfaces, blow/vent servo, and sporadic spinning of the screw. It also happens with a brand new Sub 10 ESC. I've been told the Mtronics UNITS fail to all stop on propulson when they loose signal. I think it would be good for Mtronics to publish how the failsafe in their equipment works. I did find I had a worn out APC-4 and replaced it with a spare I had. The Novak Rooster I have in Trepang's cylinder poses no problems, but there's an ADF in there, too. I used to have it in a Subsafe equipped cylinder where it worked as advertised. The Novak is relatively ancient and apparently bulletproof! I had a Hitec EZX-R in my Marlin that wouldn't play right with the PBU gear all the time. I've since abandoned the original Marlin cylinder and it's equipment for something much more reliable. I can only say that some experimenting may be in order so that you find a good combination that works reliably.
Good luck, young Jedi!
"If you ignore the problem long enough, it will go away. Even flooding stops eventually!"