Your Jetsetter should stay warm. I'll admit that 34 degrees is cold. Who am I kidding? 64 is cold to me!!
Do this simple test on your next soak: turn the heat up a couple of degrees, and then turn on the jets. Put your foot over the return fitting. It should feel hot. It should stay that way even with the jets on. If not, then you may have a simple jumper setting out of place: there are jumpers to allow the heat to run at any time on a 220 spa. It's possible that this jumper did not get switched. If that's the case, then the heat would go off as soon as the jets come on.
The speed with which it reheats sounds like it is hooked up correctly to heat on 220, it just may not be doing it with the jets. That would be possible if the installer changed the power block jumpers but not the circuit board jumpers.