this took a while.
i finally managed to trace down a heisenbug (with totally unrelated error messages and with a behaviour almost impossible to debug). however, I was able to compile the BTrack C++ libraries with a CLI wrapper to make it easily usable in .net an therefore in Gamma and appears to be stable.
you can find the BTrack beat tracker now in VL.Audio.GPL nuget with a helppatch. please test and report your findings.
enjoy!