Multibody MSL models containing springs don't simulate

[Bruno Scaglioni]

Using MSL 3.2.1 and the last nightly build for windows (13047)
Models from Multibody.Examples containing springs compile but simulation doesn't complete.

the first tested model is:

model SpringWithMass
 extends  Modelica.Mechanics.MultiBody.Examples.Elementary.SpringWithMass;
end SpringWithMass;

output file log contains this:

....
2 : assert(noEvent(spring.lineForce.length > spring.lineForce.s_small), "
The distance between the origin of frame_a and the origin of frame_b
of a LineForceWithMass component became smaller as parameter s_small
(= a small number, defined in the \"Advanced\" menu). The distance is
set to s_small, although it is smaller, to avoid a division by zero
when computing the direction of the line force. Possible reasons
for this situation:

• At initial time the distance may already be zero: Change the initial positions of the bodies connected by this element.
• Hardware stops are not modeled or are modeled not stiff enough. Include stops, e.g., stiff springs, or increase the stiffness if already present.
• Another error in your model may lead to unrealistically large forces and torques that would in reality destroy the stops.
• The flange_b connector might be defined by a pre-defined motion, e.g., with Modelica.Mechanics.Translational.Position and the predefined flange_b.s is zero or negative.

");
...

and the result is this:

record SimulationResult
    resultFile = "c:/temp/TestPolimi.MultiBody.MSLTest.Failed.SpringWithMass_res.mat",
    simulationOptions = "startTime = 0.0, stopTime = 1.0, numberOfIntervals = 500, tolerance = 1e-06, method = 'dassl', fileNamePrefix = 'TestPolimi.MultiBody.MSLTest.Failed.SpringWithMass', storeInTemp = false, noClean = false, options = '', outputFormat = 'mat', variableFilter = '.*', measureTime = false, cflags = '', simflags = ''",
    messages = "warning | Error solving nonlinear system residualFunc10 (size 1) at time 2.35831e-007

info    | model terminate | Simulation terminated at time 0.002
...