Hi My non-linear model is a clevis

[LoSV4]

Hi
My non-linear model is a clevis type assembly, loaded in the axis. Contacts are set to frictionnal, factor 0.1
I'm experiencing a sudden very local stress divergence while refining the meshing with the convergence tool.
The stress maximum looks very local, on several nodes, and in this area, the surface looks “bumpy”…
What can be the reason for this, and what should I change to obtain relevant results?
Thanks for help by advance.
Links for model images :

http://files.engineering.com/getfil...4951-98bc-e4623bf53fdd&file=Complete_assy.png

http://files.engineering.com/getfil...7a7-d18ce4e1b8e2&file=Convergence_history.png

http://files.engineering.com/getfil...5-007c-475a-84cd-873e76fccf43&file=Clevis.jpg

http://files.engineering.com/getfil...d4-4cc0-944a-c27c309b9907&file=Max_detail.jpg