Ok, so Reenforcements Delayed can also appear, when you have UMOB:true? Because it never occured to me and I recently reinstalled eb and always had UMOB:true before.

Reinforcements that are delayed can join the battle still later.
So it happend to you, that you got the message (Reenforcements Delayed) and they actually came?
We're not talking about reenforcemnts, that are lingering at the edge of the battlefield to join you when one of your units routs/dies.