Strange issue in Gibraltar Fort??

I'm playing as Great Britain and I built a fort in there but when I'm defending Gibraltar fort and I sent my armies go down from the walls through the ramp the most of soldiers dies in end of the ramp.

For example, if my army has 80 soldiers when they get in the end of the ramp they died till rest a few soldiers and then they rout away.

What's happening??

You are not the first one to report it. There is no known fix right now.

Thanks irishron... so if I'm not the only one who have this issue why doesn't CA fix it??

This never happens to me when I was playing Empire and Napoleon is based on Empire, right??

Empire and Napoleon both use the Warscape engine but after that the differences begin. They keep saying Napoleon is more optimized than Empire but other than multicore use don't really say how. The only reason for the uniforms to change color that way, and I am going back before Rome Total War was born, was either a memory leak in the game's graphics code or in the graphics drivers.
CA will deny it and blame it onto AMD and Nvidia, but I think it's the way the graphics pipelines are optimized in the code. I don't have the programming skills to refute their claims but this is what 22 years of playing pc games tells me.