Any advice to bugged UMF?

[Frozic]

I find the plain uber monster fest the easiest to defend solo HCNM. But the problem is that every time I play this map, one copter with ogre just keeps flying around near the edge of the map and never comes to my towers. First time I played the map this didnt happen and I completed many waves, but now I cant get past first or second wave because of this.. (I might be able to put down some turrets to shoot at them, and if lucky, they hit it enough to kill it before the time ends, but usually I run out of time.. and anyway it doesnt really matter do I kill it coz there's always a bugged copter in the next wave) Any tips?

[Road]

if you can hit it once they usually attack use a ranged dps try to hit it with somthingor get some friends in there.