Why is mesh animation lathering in dragonbones/spine?

Question

Raster graphics

When I animate a picture with the help of a mesh, it happens that it loses quality for a millisecond and becomes super soapy, it is very striking.
Can you give some info on how to avoid this and why this happens? I honestly googled a lot but couldn't find it anywhere. I really need help and explanation.

P.s. An animator who does not have the time and energy to explain to the stupid me why this is happening said that you need to make a texture with a size with a margin of quality. It is impossible to increase the stretch by more than 20%.
I didn't understand him at all.