The notes for all LS-DYNA releases can be found here. Use those notes as a guide to track down the responsible change. Between the releases you mentioned, there have been many fixes and changes to *CONSTRAINED_LAGRANGE_IN_SOLID, and only a few changes to the EOS. https://ftp.lstc.com/anonymous/outgoing/support/FAQ/ReleaseNotes/Also, you should run all of the releases between R7.0.0 and R11.0.0 to further narrow it down, e.g., R8.1.0, R9.1.0, R10.1.0, etc.. Those executables can be downloaded here:http://ftp.lstc.com/user/ls-dyna  (for SMP executables) http://ftp.lstc.com/user/mpp-dyna (for MPP executables) Also re-run with the latest release R12.0.0 since that should contain the most up-to-date changes.https://forum.ansys.com/discussion/comment/101304#Comment_101304

I guess you are right. It seems that CONSTRAINED_LAGRANGE_IN_SOLID is a tricky keyword to use, and I should be more cautious using it.nnThanks for the help.n