As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT ATTND REPORTED THAT THERE WAS A STRONG THUMPING SOUND ON THE FLOOR OF THE FWD GALLEY UNDER THERE JUMPSEAT (AIR RETURNED BACK TO PDX) / CLEARING DMA LG PG 0418863 R&R VALVE PER AMM 21-27-05 OPS CHECK NORMAL CLOSING# 31611 PN OFF/ON: 20798-01 SN OFF:0246986 SN ON: 0046916