Bugs with tzeetch units

oftenly i've found problems with my chaos armies ranged units, you see half the time my hell canons sit there and say they are firing but do not actually shoot, as in spending whole battles thus.
My horrors sometimes do the same
and my sourcerers on their floating discs just repeatedly cycle the message, firing reloading without actually shooting. Can anyone tell me whats up with this?

my brother was complaining about that too, about the horrors, i think it has to do with them being on an incline of the enemy being on an incline, but i don't know the answer. it would be nice if someone could fix that.

also i found the horrors don't seem to fire if you have any units between them and the enemy. it makes them awfully vulnerable and hard to baby sit...

Test this in a custom battle on flat ground.

If they shoot then it's a matter of not having a clear line of sight to the target.