When this issue first occurred my friend and I BOTH experienced it but we were also using a couple mods. I DID test AND reproduce the bug WITHOUT any mods as well.
As far as I can see right now this seems to ONLY occur in a server environment, not singleplayer.
Also I use Headless Clients on my server and thought that may be part of the issue BUT after more testing the bug is present with or without Headless Clients in the mission.