The results may be unexpected for you, but are quite reliable.
Indeed, if you specify a maximum rotation of 3 degrees and for instance 50 mm free displacements inwards and outwards in the joints, the you obtain STOPS in joint el. 60 and 133. See attached view of the displaced pipe (displacement factor 10).
To explain the results you obtained I made a simple example in PLE.
Due to the internal pressure of 1.725 bar a thrust force ("spatkracht") of about 24 kN in the upper and lower bend is generated more or less perpendicular to the oblique pipeline section of about 1 m long. The horizontal and vertical soil springs are approximately 0.01 N/mm3.
So the simple example model is a 1 m long horizontal pipe with free ends and soil springs as mentioned. Same diameter and wall thickness as the "zinker". At the one end a force of 24 kN upward and at the other end 24 kN downward is applied.
The results are as follows: A displacement at the ends of about 500 mm (in opposite directions) and a rotation of 1.256 rad = 72 degrees.
So if the max. rotation is less, the a STOP results for tensile resistant joints.
