HistoryWalker in CHECKPOINT mode cannot walkBackward to get last update of task and then hw.walkTo(0) to effectively reset itself. SLA Timeline will show NullPointer ExceptionDescriptionHistoryWalker in CHECKPOINT mode cannot walkBackward to get last update of task and then hw.walkTo(0) to effectively reset itself. SLA Timeline will show NullPointer Exception.Steps to Reproduce Create an incident and update the record a few more times such that the sys_mod_count is greater or equals to 2. Run script below: var gr = new GlideRecord("incident"); gr.get("<SYS_ID>"); var hw = new sn_hw.HistoryWalker(gr.getTableName(), gr.getUniqueValue(), "CHECKPOINT"); gs.log("LAST UPDATE"); hw.walkBackward(); printChangedFields(hw); gs.log("AFTER UPDATE"); hw.walkTo(0); printChangedFields(hw); function printChangedFields(hw) { var walkedGr = hw.getWalkedRecord(); var fields = GlideScriptRecordUtil.get(walkedGr).getChangedFieldNames(); gs.print("Fields changed at update " + hw.getUpdateNumber() + " were:"); for (var j = 0; j < fields.size(); j++) { var fieldName = fields.get(j) + ""; if (fieldName !== "variables") gs.print(walkedGr.getValue("sys_updated_on") + " " + fieldName + "=" + walkedGr.getValue(fieldName)); } var variables = walkedGr.variables; for (var variableName in variables) { if (variables[variableName].changes()) gs.print(walkedGr.getValue("sys_updated_on") + " " + variableName + "=" + variables[variableName].getValue()); } gs.print(""); }WorkaroundTemporary work around is to change sys_properties: com.snc.walker.default from CHECKPOINT to HISTORYRelated Problem: PRB1990465