Bug reports.

This is not a bug. When the AI controlling human troops (in auto-battle or with an uncontrolled ballista) decides it's time to retreat, it suggests this to the player. When using Blindness/Berserk, keep in mind that even an uncontrolled ballista can allow the enemy to escape (it depends on luck: the AI will decide whether it's time to retreat or not). After agreeing to retreat, there may be another message offering to buy off the enemy instead of retreating, but this happens much less often.