As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED. UPON COMPLETION OF W/C 78C21033001 FOUND MESSAGE CLASS 01 DOOR 1 LT PRIME WELS CONTROL UNIT FAULT. PERFORMED FIM DMC -B787-A-33-50-F1-37A-421A-A MAINTENANCE MESSAGE 33-11221. REPLACED WELS CONTROL UNIT, IAW AMM B787-A-33-51-07-01A-520A-A/720A-A.