Capturing Central Square - Walk or charge??

[Lord of the Isles]

I've noticed this behaviour and other strange stuff too. Last night I had a new one. Egyptians have two units under the flag, Light Cavalry and Axemen. I bring up two units on one approach road and one unit on another one, two of them Persian HA and one mercenary Camel Archers. All three halt just outside the square (this was a 12,000 - 24,000 city so lots of room) and pour arrows into the Light Cavalry. Yes, I know, it's cheesy.

The last LC dies but my HA aren't on fire-at-will so I select them, one after another, and right click on the Axemen (who are in range). Nothing happens! All three units sit there, no firing animation nor change on their unit cards. Wierd. So I decide to move them closer. I cannot. All three units ignore all orders, even when I try to retreat them back down the approach road. The animations are still milling around as usual, blowing their noses, sneezing or whatever but they refuse to carry out any orders.

Eventually I hit upon moving other units into the square. Around the time they pass through the "frozen" three units, I decide to Ctrl-A (select all) and charge the axemen. The frozen units obey along with the others. Wierd.