This is not a new bug, it has been in existence since the release of AoK as far as I know.
When you want to attack gates with melee units and click on it, the units only attack the side of the gate that you right-clicked instead of spreading out across the surface of the gate and attacking it. Similarly, if your units are attacking the gate on one side and you right click on the other side, the units stop attacking on the left side and start attacking on the other instead of spreading out.