Crop bug
The crop bug is where your city starves, but even after you add plenty of crop to the city, your first attack is still at half power.
This can cause a loss of troops or even a complete loss since your troops aren't killing as fast as they should.
There is a way to work around the bug, but the bug still needs to be fixed since it's costing people crop and troops.
The workaround.
Add crop to the starved city.
Switch between cities, or log out and log back in.
As for it costing crop that it shouldn't.
As an example, if you buy 100K worth of crop for your starved city, switch cities and back, that 100K crop suddenly becomes about 90K. Somehow, you lose a lot of crop to get it to reset correctly.
If someone is buying crop with coins, this may be also costing them more coins than it should since the rate of crop consumption after a starve is much higher than it should be.