Press F2 to find if the non-convergence is due to "old state open new state closed" or "sliding error" type. If it is case one, then the non linearity is the gap in restarint, if it is of type 2, the non linear effect is Friction.
For type 1, see if gap can be removed, for type 2, see if Friction factor can be removed( I am personally against changing the default friction stiffness).Sometimes you can get both 1 and 2 type.
This is based on "how to solve the problem in hand" type cookbook solution. I want you to throughly undertand the science behind this non -convergence.
Regards
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anindya