When playing "Signal Lost" on normal difficulty and you're killed, you get given the option to restart from a checkpoint. This first checkpoint is after you've finished your conversation with the lieutenant and are off the beach.

If you die during the mission you're offered the chance to restart at that checkpoint. If you do so, you're presented with the good old "you cannot play/edit this mission it is dependent on downloadable content that has been deleted" error, followed by a very long list of "missing content".

After having dismissed that error, you're taken back to the start of the mission - to see the quote splash screen, go through the cut-scene and start the mission back on the beach. However, instead of occurring as designed, the camera remains fixed upon the sea (from eye-level), with no HUD, rendering the mission unplayable.

In order to play the mission again, you must exit the mission and then restart it from the "campaign" main menu.