Answer
Check the base table's own ROWKEY column configuration — for a custom-field table like JT_TASK_CFT tied to a base table like JT_TASK_TAB, this specific error means the base table's ROWKEY column isn't correctly set up as NOT NULL with a DEFAULT of sys_guid(). IFS's own documentation on ROWKEY details (part of the upgrade-preparation/installation roadmap docs) covers how to correctly repair a base table's ROWKEY column configuration when it's missing or misconfigured like this, which is the underlying fix rather than anything specific to the event action itself.