Apparently, if you send your army to auto-rob and your army is set on low/mele, it is not a glitch if they never return home. I lost about 20k troops during an auto-rob incident a few weeks ago. I sent my full army to auto-rob a farm in my contour. I checked back in a few days later and noticed my army was still in that same farm, just sitting on the storehouse. 50 footpads were taking shots at my powerful army, slowly killing troops with each shot.

I have no idea why my formation was set to low/mele, but that's beside the point. I can understand that I would have lost some troops during the auto-rob, but since my army never engaged with the marauders, I would have expected my army to finish robbing the storehouse and then go home. This never happened. I entered a support ticket and they said this is not a glitch. YOUR ARMY WILL NOT RETURN HOME IF YOU ARE SET ON LOW/MELE. I find this completely absurd! 2 things should have happened here.

1. Army finishes robbing and returns home without any attacking
2. Army finishes robbing and as it moves towards gate and on top of marauders, marauders die instantly. Then, army returns home.

In this case, army finished robbing but never made an attempt to go back home. Support has refused to restore any troops despite my repeated appeals. Here is their last response.

Hello!
We have tested your problem.
Your army have a low aggression and melee attack. It is not a bug. Your army is waiting, when the enemy will come in his field. We don't restore army in this case.