Here's a good LOS problem that has happened in our last two games.
A positions himself has a clear line of sight onto B going across a few diagonals, ready to blast B away.
But C partially move his mech to block LOS between the dots, no problem you may think, I'll shoot C instead.
Now the problem is that C cannot be shot at as there is a corner building blocking LOS between the 2 spots.
So A can now no longer shoot as he can't gain LOS to either - pretty stupid huh?