Strange Population Bug

I've just made it to Lvl 18 and I have the resources to add more troops to my army, but the game won't let me. I have enough space for the increase in population, but the values just turn red when I try to add more than a certain number... I also added 25 Recruits to my army to attack a bandit camp before that but, now that they've returned, I can't replenish the troops I've lost!

Is there a hidden population cap the game doesn't display to users?

Every normal general can hold 200 units. More will not be added.

If you loose a battle the general is "wounded" and needs to heal.
With the normal general this will take 4 hours. In those 4 hours you can't add units.

If you are not in that 4 hour healing period and/or you are not on the 200 unit limit count, I would suggest to contact tech. support.