I do not know what exactly it is, but when I let my base run unattended for 100-200 cycles, I often find several suffocated dupes in space, for no apparent reason. I did though they get buried in Regolith and put in timed doors to keep them away, but that does not seem to be it. I rather suspect they somehow go on a fetch task with Oxygen already critically low and then do not make it to safety. This has never happened to me before and seems to be an issue with the current preview changes. The first attached save is a state before it happens, the second one is the same with 3 dead dupes some 150 or so cycles later, no other changes. This has happened several times to me now.
Steps to Reproduce
Let first save run for 100...200 cycles, find dead dupes in the left space area where the autominers are.
This issue has not been confirmed by a developer yet.