I've managed to do a couple on my own. But a number of times I have done a large amount of damage to the enemy on checkpoint 1 out of 5 or something similar and then they will just warp halfway across the area it will jump up to checkpoint 4 of 5 or something and they'll get away. I haven't even been able to catch up to them on my ghost a few times! It's ridiculous! One managed to pop up when I was doing the capture the spire mission on mars (for heroic daily) I was in the interceptor railing him with the rockets and got him down to 1/3 health when he just vanished and appeared a good distance away, I managed to catch up to him and shot him a few more times and then he vanished again appearing AT THE FINAL CHECKPOINT so I got bronze :/ I wouldn't mind if he had ran away but to just vanish like that.... He was a Cabal Centurion not a vex capable of warping and he didn't even use his jetpack, he just vanished.... This has also happened on Earth with a Hive Knight, Mars again with a Psion among other times that I cant specifically remember.