Description: Cannot end the turn.

Steps to Reproduce: 

We have tested two games and we believe this is what causes the bug:

1. Player A attacks player B unit.

2. Player B retreats.

3. Player A attacks player B's retreating unit again.

Player B reported that he did not see a notification about his retreating unit being under attack. 

Then everyone gets stuck on the current turn. Players see the loading icon over the end turn button
but the turn never ends.

Attachments: Sorry, the autosave got overwritten.