Overlay bug in Prototype
Applying one overlay is fine. However when you move on to another page and apply a transition, overlay is already selected. It should just add another overlay, but it doesn't, you have to switch to a different type of transition, then switch back to overlay for it to work. If you don't do this, in Preview, the overlay appears over a black or white background as if overlay wasn't applied at all.
Not a huge problem but wastes a bit of time.
Vertika Gupta commented
Thank you for reporting us. Able to reproduce the bug in my machine also, Filed a bug and will prioritize it.