I'm trying to do the mission The Black Site, where you have to hack the bases computer. The underground structure has 3 tunnels that require defending. If I try to place mines they magically disappear now, this was not always the case because this is exactly how I beat this level in the past. I can place them on one entrance and by the time I place them on the 2nd the 1st tunnel is clear, poof, they've vanished. This Tier mode is frustrating enough, why do we need to be dealt a stacked deck??
And it gets worse, despite any defenses I set up, twice a truck load of rebels destroys my mines alerting the enemy, why are they entering a Unidad base?? Then a truck load of Unidad spawns in the center of the tunnel, avoiding the mines completely. I'm going to write this mission off as undueable at Tier 20!
There are lots of Things that are not only difficult or extremely difficult, but just not fair and frustrating. What you described for example. Or the teleporting Enemies that penetrate Concrete Walls while my AM Bullets get stopped by a Stack of Tires.
Don't get me wrong, I love good Challenges. When they are good designed and fair. Or when there is more to do than the same few Missions over and over.