ah that was definitely a bug in the pseudo-inverse code
a more sensible cutoff for the Moore-Penrose pseudo-inverse also helps somewhat
Lots of debug output, trying to chase two issues that may be related.
- lack of convergence in task when constraints trigger, even though
  there should be enough DOF left
- bouncing chaotically off of constraints, sometimes.

Going around in circles, need to sleep. And discuss with others.