I remeshed the model with Tet elements. To my suprise, the miniumum quality improved from 0.30 to 0.36. There is no hourglass energy now. I was taught that tetra is a trash element and can be used only as a filler. Am I mistaken ?.Anyway, the problem of oscillatory motion persists. It appeared when I changed the Maximum Offset to 0.2mm in the two bonded contacts (threads), because some elements on the thread were not involved in the contact, they were not detected. This Maximum Offset seems to be essential for proper contact enforcement.nArrayI thought the problem could be due to the other frictional contacts, however everything looks fine there, friction coefficient set to 0.05.nBoth the piston head and the crankshaft move smoothly, without oscillating.nAny ideas?n