As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD - FLT 528 - AFTER TAKEOFF DURING CLIMB-OUT OF ORD, FLAPS WOULD NOT RETRACT FROM 18 DEGREES. FLAP FAULT AND INOP CAPTIONS ILLUMINATED. AIRCRAFT RETURNED TO ORD. CORROECTIVE ACTION: PERFORMED CLEARING PROCEDURE AND SAFETY LANE 2 CHECKS. OPS CHECKS NORMAL.