RE: ***WARNING - INSTABILITY AT JOINT 15 DIRECTION = MY

You can simply use partial moment release:

MEMBER RELEASE

27 START MP 0.999

27 END MPX 0.999 MPY 0.999

30 START MP 0.999

30 END MPX 0.999 MPY 0.999

29 START MP 0.999

29 END MPX 0.999 MPY 0.999

31 START MP 0.999

31 END MPX 0.999 MPY 0.999