Replace the @TimeStamp with actual time during a bulk Filebeat Send

ISO8601 uses a CasualISO8601Parser and that defers to joda for what ISO8601 means. joda does not agree that ' 03-MAR-21 03:46:10" is ISO8601 compliant.

Just change your date filter to have the actual format

date { match => [ "timestamp", "dd-MMM-yy HH:mm:ss" ] }