As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURNBACK, HAD MASTER CAUTION WARNING WITH L/E SLAT ASSY LIGHT ON EICAS AND L/E LT. BOTH FLAP NEEDLES MOVED UP TO THE 1/2 DETENT MARK. PSEU BIOTE FAULTED S301. FSEU BITE NO FAULTS. REPLACED S301 PER MM. TARGET GAP OK. OPERATED FLAPS/SLATS ALL NORMAL.