In any case, using Filters > Animation > Unoptimize will create the equivalent animation with complete frame replacement from which you can create a WebP that will work correctly everywhere (adn strangely in my case, is also smaller).
In any case, using Filters > Animation > Unoptimize will create the equivalent animation with complete frame replacement from which you can create a WebP that will work correctly everywhere (adn strangely in my case, is also smaller).