First of all, this was reported before.
Product and version: FMP16
OS and version: macOS 10.13
Hardware: MBP 13" Retina late 2013
Description: a WV with a Base64 encoded animation (from animated GIF OR SVG) won't work when using 'New Window' script step
How to replicate: see example file
Notes: some Animation might work when opened via the Layout Manager
Please check the example file:
Thanks to Daniel Wood - Digital Fusion. I was using his example file. He put this any further by using a SVG-File.