Is it why Q Team was in Hanoi?
Back in 2001, some members of the Joint Task Force on MIAs started talking (in bars and coffee houses, not to the press) that they knew men were left behind after 1975 / fall of Saigon.
Then they had a little helicopter accident.
https://www.dpaa.mil/News-Stories/Recent-News-Stories/Article/715983/dpaa-remembers-fallen-comrades-on-15th-anniversary-of-helicopter-crash/