Hmm, I'm not positive if I know what you mean about trouble, but, the pitch tracking algorithm in the Dubterranea is the same as in the FMeron, which most people have had good results with. The synthesis side is a lot more "correct" than the Subterranea - Dubterranea generates real saws and triangles, whereas the Subterranea uses audio-rate switches and simple filtering to create something similar to a sawtooth, but only gets close to a proper saw in a small frequency range.
This post makes me very confident that I will get along just fine with the DubT's tracking; I find the FMeron to be quite reliable, even on my low strings. Can't wait to try it out!