id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
4494	Incorrect/inconsistent nonlinear solution during simulation	crupp@…	somebody	"See the attached model in Loop.mo and the attached figure showing the problem.

This model is a four-bar linkage using a RevoluteConstraint joint to break the kinematic loop. At around 3 seconds (in the figure), the position of one of the hinges makes a large jump for no good reason. There is also some chattering between two different solutions.

I suspect there is some issue with the nonlinear solver since it is alternating between the correct and a different (kinematically admissible, but kinetically inconsistent) solution. Looking at LOG_NLS, the values of the iteration variables jump unexpectedly soon after 3 seconds. With LOG_NLS_V, there is a point at which the ""System extrapolation"" values are dramatically different for no reason, which changes the x0 values and the subsequent solution.

The locations of the jumps change with different solver tolerances. It is easy to see the effect if you simulate with 3D visualization."	defect	closed	critical	Future	Run-time	v1.12.0	fixed