Units vanishing from the map. Specifically in this case was my scout unit.

I tried clicking into a battle outside my movement--which showed a preview of the battle. After this the unit then simply vanished. I managed to trigger this again while previewing another battle--and in the second case I experimented by completing the previewed battle and my unit was still invisible. Note; I could still target both by clicking on their occupied hex, but his unit model was gone.

Hope this helps!