Pinball Radius
The Pinball radius is the search distance used to find and keep contact pairs (which nodes check which faces). If pinball is too small, nodes simply don’t “see” the other surface; contact forms late or drops out. If it’s too big, you can pick up the wrong faces.
Bolt Head to Link Face Contact
Pinball is set to 3mm for the 2.5mm surface elements. General rule is 1-2x local element size.
Bolt Shank to Link Hole Contact
The pinball is manually set to 5mm. General rule is initial clearnace + 2x local element size, 0.25mm + 5mm, so I selected 5mm.
Initial contact information says the pinball is 0.25mm, and this is why it is detected for initial conditions because adjust to touch is on. But during the solver as the bolt shifts, the contact is lost because it can’t see the other face due to the original programmed controlled pinball radius of 0.25mm. During loading, if the shank separates slightly and re-contacts (or slides/tilts), the solver still needs a reasonable search radius to keep the pair active and robust.
After this change, this contact did not fail during solving.