Looks like a LOX leak caused the failure of the latest Skylink second stage. Heavy ice build up then a RUD during the planned second relight.
Here are two minutes of the SpaceX launch stream where the ice build-up began…..
The initial issue began immediately after the MVAC chill callout was made. You can see what may be LOX swirling around a grid fin….
Upper stage restart to raise perigee resulted in an engine RUD for reasons currently unknown. Team is reviewing data tonight to understand root cause.
Starlink satellites were deployed, but the perigee may be too low for them to raise orbit. Will know more in a few hours.