Me, as Romani, fighting the Ptolemaioi superpower over Kyrenaika. I have 5 nearly full stack armies. They have 2 full stack armies (of which 1 is in besieged Kyrenaika) plus about 1/2 stack with another 1/2 stack reinforcements coming in 1-2 turns.
I decide to end turn. Of course, all 2.5 stacks attack my besieging army. I chose the placement in a forest, hoping that trees will disrupt phalanx formation (which of course didn't happen). Battle begins. I have my besieging army and another army as reinforcements. To my dismay against my 1200 man army which is my only army present at the field, they throw their besieged army 1700 man plus 1400 reinforcements army plus around 600 man their half stack. If I would be able to bring all my 5 armies onto the battlefield, I'd wipe the floor with them, but I'm allowed only one army at a time and a small trickle of reinforcements when my units rout. Unsurprisingly, I eventually lose, after destroying 1/2 of their total armies.

I decide to give it another try and reload. I immediately assault the city (spies have 100% of opening gates), but instead of going for the city, which I have no chance of taking with 1700 klerouchoi, klerouchoi agema, galatian heavy swordsmen and other niceties packed inside, I go for their reinforcements. I move my army to meet their 1400 man stack. After a long battle and losing 30% of my army I annihilate them. Then I send some troops to attack that 600 man army that is wandering around. this time it's far shorter as those 600 man were led by a captain and not 2x generals like the first army.

All in all, I nearly completely destroy their 2 reinforcement armies while losing 40% of my own army. Of course, there's no reason to attack the city with what I have now. So, I let the time to expire and get a clear defeat result. To my surprise I heal no one while the destroyed 1400 man reinforcements army somehow had 400 man left, while they certainly shouldn't have more than 100 after a thorough beating I gave them. I close the results and get a "heroic death" message. I think "What the hell?" My FM was alive and well at the end of a battle. But to my shock and dismay, the whole stack of like 800 soldiers simply disappears, and I have 4 armies, instead of 5. I simply closed EB after such a blatant act of cheating by the AI and will probably have to revert to console to resolve this battle :(