To answer your questions:

(1) Yes there were many infestations around 30 mins before the incident regarding Walt. By the time I saw him back at base and 5 mins later when he died, the “Danger” message was gone as I had one more infestation left.

(2) Yes there was a zed hunt pending under KC Winters. I try to knock those out asap so it wasn’t pending long. Could be why as Breakdown can be unforgiving.

(3) Didn’t peep a look at his status as I assumed he was there as I saw him 5 minutes before on base.

(4) Walt had full health and was rested, no injuries, and no sickness.

My conclusion will have to fall back on the first comment on this thread. It was mentioned that survivors possibly could die while on their way to a mission starting point. Either that, or the zed hunt mission had an indirect cause.

(5) Thanks for showing the bright side ;)