Busqué en google en inglés y encotré este tema que no puedo poner el link directamente.
GIF Animation - what affects speed?
Cita: A little update: it seems that this animated gif banner ad was only problematic on laptops -- and the only way I can make sense of that fact is assuming that graphics cards for LCD screens have trouble handling either a high frame count or lots of timing changes in an animated gif. Does that make any sense?
Anyway, I experimented and found a way to cut the total frame count from 70 to 50 and eliminate most of the timing changes. Now everyone is happy with the results -- the new version runs at normal speed on both laptops and desktops.
Intentare seguir el consejo de reducir el numero de frames y no tener mucha variacion en los tiempos del gif.