There is an issue with the way the new Overlay is drawn in 2D output images.
You may try the sample from Ruby API documentation, enable the overlay and save say .png. The “Hello Overlay” will be drawn twice.
Overlays appearing in thumbnails (scenes, files) and exports was not intended. It’s considered a bug that we’ll be addressing.
By the way, it’s better to report API issues in the GitHub issue tracker than the forum:
The issue tracker is more actively monitored and we have automation that logs them into our internal tracker.