It seems that viewer can't handle animated .webp files properly. when one such file comes across, the viewer freezes on it and does not respond to scrolling, only manual changing a file in lister helps.
and the right button menu for these files is not from Opus, but as if from IE
We don't support animated WebP. It's a completely different file format to WebP for some reason, and more trouble than we think it is worth given current adoption (which seems unlikely to increase, with other even newer and shinier formats now replacing WebP).
(There's a viewer plugin SDK, and source to the existing animated GIF viewer, for anyone who disagrees and wants to put time into it.)
