I have assembled and calibrated my Bittle. Having it move into poses like Stand, Rest, or Calibration works without problems. However, there seems to be a serious issue: Whenever Bittle starts walking, it will fall over quickly and predictably. Also, when selecting the action "Say hi" from the mobile app, at least one of the servos started "screaming" and wouldn't stop. I had to turn off the power. Did I end up getting at least one bad servo? How could I tell? Is there an easy way to move individual servos into positions that are outside the limited calibration range? What else could be going on? What kind of test(s) should I perform? Thanks a lot in advance for any tips!

Which OpenCat branch (main or 2.0) is currently recommended for Bittle? And what is the main difference between them?