The Fatal Error map is virtually a square so is fairly maneuverable however cover is limited and not situated in good places. The best thing to do is to face the spawn point head on. Kill some of the faster enemies and retreat a little way. At every platform are some large crates that make good places to strafe around. If you move between these during the fight, you will be fine.
The first wave of enemies are Collectors. In this little lot are two Praetorians and a lot of Abominations. These can easily pin you down allowing the Praetorians to finish you off. If you become encircled, use grenades and explosive powers to kill/stagger them and run like mad.
Your teammates will probably die a lot in this match so only revive them if you need the distraction to escape. If you use no more than two Medi-Gels per round (provided you have the maximum 8) you won’t run out. Watch out for Possessed Abominations as they can nuke your entire team.
Aim to stagger the Praetorians out of the air to give you some breathing room. This can be done with a high-powered shot to the face or a powerful combo/explosion. Don’t worry about the score unless you particularly want to see how many points you can achieve. This is the challenge to do so.
The next wave of enemies is the Geth. There will be Geth Primes shooting their lasers of death across the map and firing their turrets in unfathomable places just to make things even more annoying. Luckily, Primes are slow so you can escape. Pick your moment in between the cannon pulses and then break cover and run away.
Take out the Primes first as otherwise your squad has no chance of survival. Also check your flanks now and then for enemies that may have averted your attention. If you have Sabotage, remember that the Geth are especially vulnerable to it.
Cerberus will appear next; a cohort of Atlases and Dragoons being your opponents. Dispatch the Dragoons as soon as you see them because they will make life very precarious for you. The Atlases won’t be a problem on their own.
Reapers are the last enemy to arrive. The only enemies are two Banshees and a lot of Husks so this round really is nothing to worry about. Pound the Banshees using biotic explosions and headshots, while killing Husks that get too close.
The last round is by far the hardest as all factions are thrown in together. A Possessed Praetorian will also be in the mix as well as Banshees, Primes and Atlases. The Prime and Praetorian should be your focus as these pose the greatest threat because of their long-range capabilities.
As soon as the enemies spawn, throw everything you have at the Primes. With those down, aim for any of the enemies you can see, particularly if you can kill them before they have a chance to move. Stay behind the large crates and you can even circle them to keep a wall between you and an enemy.
Revive your squad as soon as they go down because you’re going to need them, if only to provide some cannon fodder. You may find yourself in a situation where you need to choose between two paths with enemies on both. If one has Atlases, always head in that direction as you can avoid their fire a lot better.
You may also want to lure the slower enemies into a corner and then make a break for it, rushing to the next platform while they are busy looking where you last were. This can help to bunch the enemies up, making grenades and explosions more effective.
Rinse and repeat the above tactics and eventually you will conquer the level. A final email will be waiting in your inbox where Armax will thank you and give you the Assault Rifle Thermal Scope . You will also unlock the " Technical Issues " trophy/achievement.