I'm begin...
Frist. I generated MNG image by ImageMagick. May be correct. BUT!
Two. I converted MNG to MNG again, and get incorrect MNG animation (not clearing). And delay=0.
Tree. I tried same MNG, but with advmng. I get: same effect with blend (not clearing) and loop=1.
All convertors and optimizers can no optimize MNG. Because MNG images probably invalid.
Help me generate and optimize correct MNG image.
Also I used flags "-dispose Previous" and own delays per frame.
Why need for me MNG? I ported libmng (Emscripten) to JS, and need test with valid MNG images. Also I can use JNG, but this is not interest now.
About JNG, I have even two library: Emscripten libmng and parser for JNG (hack).