AG.SYNAPSE, Final Mission (The Scientists' Extraction), right before turn in. (Sorry I didn't screen shot this, but when I tried different things to get out of this, I fell through the world and died and it respawned me, so I didn't take shots of it.)
TLDR: Spot at turn in area that at first appeared to be quicksand (couldn't move and was stuck in the ground from the waist down) but then when I tried to go prone, it put me under the world and I died.
I had completed all 3 missions before the final one, so that there would be the least amount of extra hindrances. I was doing this mission almost entirely stealth, and cleared the entire campus (including disabling all the SAMs and turrets instead of destroying them) and please note, this is the part that took the longest and is pretty frustrating that I got reset to the bivouac above the mission with everything completely respawned/reset. Time to do it all over again.
I killed everything (with the help of 3 AI teammates) in the area and disabled all turrets/SAMs, so that when I finally triggered all 3 hostages, the escort part would be trivial. Silly me, thinking I'd get away easy! I triggered all 3 hostages. I walked their slow behinds to the helicopter that was on the pad there at the campus. I got in and waited for all 3 to board. I flew to the point where I was supposed to deliver them. I landed at a point SE of the building at that location. Standing to the SE of that building and facing it, there is a sort of trail going up to it. I landed the helicopter slightly to the right (NE) of that road. I hit e to get out of the helicopter. It did not put me right at the door to the helicopter, but instead sort of warped me to a spot that was slightly south of the landing spot, possibly on that trail, but I think it was slightly to the right side of the trail (as facing the house). When I appeared, I was at first surprised at how far I was from the helicopter (after pressing e and not moving) and further surprised by the fact that my legs were sort of stuck in the ground. The visual of the situation actually looked like I was sort of in a foxhole or some such, because my waist appeared slightly lower than the ground level where I was. It was like I was in a hole that would have been 6-12" deep, and my waist/legs were under the ground in said hole. I tried moving in different directions and hitting space / ctrl to crouch or hopefully mantle out with no luck. I then tried pressing c to go prone and then I was under the earth. It had sort of a greyish look to it (compared to the browns and greens of the dirt and trees above me) and I started to fall a little and then died and respawned.
I flew a drone back over to that location (since it was faster than running back and I wanted to recon the place before walking back into a death trap) and couldn't see anything that resembled the sort of shallow hole I was stuck in. This is also how I got the directions I listed above to help sort of show where it was (roughly) that I got stuck. I'm going to do the mission all over again now.
I am using Windows 11 and can provide computer details if you require them.