I decided to keep playing after one of my duplicants died; normally I reload and rescue them.
Just after she died, the rest of the duplicants became stuck running or climbing in place. They would still respond to move commands and navigation was fine. Based on my experience with the game, I believe they were stuck in a "finding path loop" - where they're running or climbing to get somewhere but are calculating how to get there. I've haven't seen this behavior recently, so it's not due to my hardware or having too many paths.
So I said, let me reload and see if the issue remains. Well the issue remained and also got worse. My duplicants don't move AND disappeared.
I can get them to reappear and move if I force them using the move command/button, but then they just keep running in place where I told them to move to. They move to get oxygen if they are out of breath, to use the bathroom, and to eat and sleep, or to mourn.
Once they mourn, they resume normal duties.
So, is it intended that duplicants perform no tasks until they mourn? This can take a while for large bases: 76/2*10 = 380 seconds (approx 6 minutes).
2 duplicants mourn at a time
mourning takes 10 seconds
If it is intended, then the scope of this bug report is that the duplicants do not appear after loading a save game and when they are mourning, or get stuck in the running/climbing animation if visible.
Steps to Reproduce
Have 77 duplicants and let one die
This issue has been fixed in either a future version or updated in a previous version.