Answer:
In principle, a calculation with RF‑FORM‑FINDING has the same requirements as a calculation without this add-on module, so the criteria for general instabilities should be checked (see "Links").
However, problems often occur with RF‑FORM‑FINDING because the form-finding process has been activated for too many elements. Therefore, you should check whether the correct (necessary) elements have been activated (see Image 01).
In the following example in Image 02, form-finding has been activated for all horizontal members. This results in the error "The stiffness matrix is singular!" (see Image 03). If you deactivate the beam members, the calculation is successful (see Image 04).
