Welcome to the world of Random Number Generators, sometimes you should win but you do not.

Roarke's Drift and Blood River are good examples.

In both the Zulu should have walked over the defenders without pause in both cases they were beaten off.

The battle predictor does not predict what will happen but what should happen. 

The RNG dictates what does happen.

The predictor is mostly right but just as most observers of a certain battle in the middle of The Pacific Ocean on 6 June 1942 found out random events can cause the more powerful force to end up crushed.

Just as the IJN was that day by the much inferior, on paper, USN at The Battle of Midway.

For the record the myth the Zulus only had spears at RD is refuted by historians that study the battle, they had rifle they had bought before the war as well as captured ones from the earlier battle that day.

The Spear thing is revisionists trying to make the win at Iswanandha look even better and make excuses for the defeat at RD. They have done the same for the Little Big Horn stating the Sioux and Cheyanne were equipped with bows and arrows when in fact they were better equipped than the 7th Cav. the amazing thing to me is that all 500+ members of the 7th were not killed rather than only half.

You know, the game is still changing pretty fast with major updates. 

When something happens, like a ship jumps out of the fleet and kills itself attacking an enemy alone because I just upgraded the flag before an attack and had it selected by itself, not the entire fleet, I just restore the last autosave (changed to every turn) and redo. 

I remember playing Zulu vs Brit in a table top miniature battle, at a con in Maine back around 1980 or so, and the dice really voiding the rule of averages... Come to think of it there was a time in Vegas were I'm sure the house was cheating .