thanks for your reply. Sure, I can provide more details: the coefficient of friction is 0.12. I haven't changed anything to the default settings of the contact so far. The number of contact elements stays nearly constant while I pull which I interpreted as a sign that the contact behaves as it is supposed to. "Pressure" and "Penetration" show similar peaks, but I assume that this is a consequence and not the reason for the "peaks". Furthermore, I tried to estimate the influence of the contact and used contact step control to change the contact to "bonded" in the last load step - this had no effect on the peaks.