Sometimes, the engineer needs to make a joint with one bolt only, especially if e.g. a hinge, a bracing, a rod, or a diagonal is expected. To model and calculate this kind of operation, you need to define a proper Model type of the member.
If you use the standard Model type: N-Vy-Vz-Mx-My-Mz for member connected only with a single bolt, the mechanism/singularity can occur or the analysis will fail.
You have to change the Model type to N-Vy-Vz in Properties of the hinge connected member.
Now, the model is correct and mechanism is prevented.