Ok, so my strategy now is the following: At the beginning of an automatic DRC fixing session we extract to .ext, then we try to fix all DRC issues. We remember all the actual successful steps to fix the DRC issues. At the end we extract again and check for any LVS/SVS regressions. If there are no regressions, we are done. If there are regressions, we have to triage the remembered steps individually to see which of them are good and which of them cause LVS issues.