Update:
After talking to Soundtraxx, they convicted me to take another look at my stall current before sending the Tsunami2 back. When I first tested the stall current, I didn't have my battery in hand yet, so I attempted to create 12.5VDC using my AC transformer and a full wave bridge. I just turned up the AC legs until I read 12.5 V across the DC legs.
I know that without any sort of capacitance the DC is really jagged, but I thought that the "True RMS" description on the Fluke meter was telling me that my DC volts were pretty close to 12.5V rms.
So I checked stall current this way, and I showed just over 3 Amps. Maybe not so bad.
However, I now know that measuring DC current this way is cheating, because at the urging of the Soundtraxx guys, I re-checked the current with my actual 12Vbattery now that I have it, and the result (as @gunrunnerjohn suspected... Should have listened closer) was actually 7.5 Amps!
So it's very possible that the Tsunami is not at all to blame here. Even though I've heard from others that the current protection circuit is tripping prematurely, in my case it wouldn't matter anyway sauce I'm well beyond the capability of the Tsunami 4400.
Oh well, I suppose I'll move it over to a different steamer at some other time and start the search for a decoder that can handle this motor.
Moral of the story: listen to the experts. It will save you time and money!
Video of the battery test attached.
