I had an interesting situation where, one minute, the preview showed the correct results, and the next, it showed incorrect results. It appeared to be doubling the King effect. Specifically:
I had two attacks scheduled to hit an enemy base right after each other. When I set it up, it correctly predicted my enemy's king effect, and the end result was me taking the base. Shortly before the attack hit, during the 'attack window', I was planning my future moves when suddenly it showed me still losing the first hit, butwith his 184 drillers stealing 104 of mine instead of the correct 61. My second attack showed similar issues, and I no longer was taking his base with that one. At first I thought he had hired a second king, but I asked him, and he said no. Sure enough, the first attack hit, and the results were the original, correct results. However, my second attack was showing similar problems with his king taking way more than he should have. Again, my attack hit, and the correct results occurred, and I took the base.
End result, things happened as they should, but it sure threw me into a panic, as all my well-laid plans were suddenly in question.