How can I avoid dropouts when using (imagemagick) `mogrify` to convert webp files to animated gif?

Using this code mogrify -format gif *.webp that I found in another forum https://superuser.com/questions/1506337/batch-convert-webp-files-to-gif-files-offline/1506428 to convert a webp file, to an animated gif...

I was wondering if anyone else experienced patches of black and/or white "dropouts", when using this method? With many files, it works without incident, but with others, such as the attached, I have to use an online converter, to avoid this issue. Are there additional filters that I could apply, or other CLI methods for this type of conversion?

Some of your webp frames have transparency and others do not. The fix seems to be to set the dispose method to none. So this works for me on IM 6.9.10.90 Q16 Mac OSX Sierra using convert. I suggest you use the more flexible convert rather than mogrify. I am not sure you can do what you want with mogrify as it wants one output per one input. Here is my command:

convert -delay 10 -dispose none tumblr_e573d6d767dd3d65d21de47fa7d16d13_4d26286c_400.webp -loop 0 animation.gif

or better

convert -delay 10 -dispose none tumblr_e573d6d767dd3d65d21de47fa7d16d13_4d26286c_400.webp -coalesce -loop 0 -layers optimize animation.gif

Give that a try and let me know if it works for you. The file is too large to upload directly. If you need to see it and my command does not work for you, then I will post it elsewhere and put a link here.