The error happened to me when using the second time on the Big Forerunner Laser

Happened to me

Yep. Can't get the Target Designator to take out the Phantom and the cannon.

Yes I had it happen to me as well.

Originally posted by jlines627:

Yep. Can't get the Target Designator to take out the Phantom and the cannon.

me too

Can someone please offer a solution?

you have got to be kidding me right now

I could get the target designator, but 99% of the time it didn't work properly. it seems to lock on only veeeery rarely, making it tough to finish the mission. what really kills the flow though, is the moment the lich appears. that just crashed my game

Yes, it could use a fix. Possibly for future updates.

you can kill it without the mac cannon. just shoot it with a sniper a bunch. it could take a while

Crashed right as I lased the first phantom.

crashe when pointing to the forerunner weapon

Yep same issues.

same

My solution to the problem of the target designator crashing the game is to minimize its use.
You should really only need to use it once to target the Foreunner particle cannon.
When the game tells you to use it on a phantom, do not use it, and the phantom will fly away behind a mountain and eventually despawn. Alternatively, destroy the phantom by other means, such as the rocket turrets on the mammoth.
When you are required to use it on the particle cannon, my solution was to hide as much of my HUD from the particle cannon as possible. I hid behind a warthog to obscure most of my perspective, and I looked for the highest part of the particle cannon that would count as hitting the target. (You can tell by looking for when your reticle turns from blue to red.) I also avoided any combat, as targeting the particle cannon while under fire seemed to cause issues.
Hope this helps anyone!