What you were expecting to happen, and what actually happened?
When doing skull damage the wraith does not always inflict death mark/freeze. Wraith is fully traited and I have confirmed that stun effect was no tin effect.
What are the steps to make it happen again?
I have not fully drilled down on the mechanic behind it but it looks like the main trigger is when the the first rank enemy dies of skull damage, at no point in the rest of the match will the wraith inflict the effects. It’s possible though less likely that a kill through death mark triggers it. I am also reasonably certain that the issue is tied to the first ran k enemy and will not replicate further down the chain. Only discovered this tonight and am still gathering data.
I don’t use video capture equipment but the bug shows pretty reliably for me so if you create the above conditions it should happen.