thank you for the suggestions. I changed the analysis settings and added the symmetry plane. Although the analysis can be solved, when 'releasing' the bending test, the specimen disappears. See the images below at this transition point:
Why does this happen?
I get the following warnings too, maybe those are related;
4) Large deformation effects are active which may have invalidated some of your applied supports such as displacement, cylindrical, frictionless, or compression only.
3) One or more bodies may be underconstrained and experiencing rigid body motion. Weak springs have been added to attain a solution.
2) Solver pivot warnings or errors have been encountered during the solution.This is usually a result of an ill conditioned matrix possibly due to unreasonable material properties, an under constrained model, or contact related issues.Check results carefully.
1) Contact status has experienced an abrupt change.Check results carefully for possible contact separation.

Changing frictionless contacts to 0.2 friction didn't help. Adding a zero movement constraint in x-direction on the symmetry plane neither.
Maybe this helps to identify the problem:

Your help is much appreciated.