I was just starting a thread about this myself. Our users are having the same issue while editing their own posts. They get a message about an “Edit Conflict”
I experienced this myself on a Wiki post. I started an initial post, then later edited it, and when I went in to edit it again, the second edit was gone. I also had the “Edit Conflict” at the bottom. (So far, I was the only one editing this particular post, so there was no user conflict)
This next screenshot is when I tried to enter a third article into a wiki post, but the second article had disappeared.
EDIT: users now telling me that they sometimes get an “overwrite” prompt, but if they click OK to that, all previous edits disappear