Custom Delta Property NAK handling is done via Custom Delta Base States.
Whenever we replicate a CDP, we have the implementing code return a Custom Delta Base State.
However, before a CDP is ever replicated, it won't have a Custom Delta Base State.
The NAK logic will ignore reverting to a Property Retirement if a Custom Delta Base State is invalid.
This means that if the initial packet is dropped, we won't revert to the initial / invalid state, and instead just leave the CDP on its current state.
The effect of this depends on how the CDP is implemented, but in most cases (especially for Fast Arrays), it could end up looking like we just missed certain properties.
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-74214 in the post.