I do not know what goes wrong, I think others should also appeared in the BUG.Relatively high probability it appears.
In the same project.
I finished the first object: Object A.
I copied object A, re-named object B. Remove bones and re-import pictures, I did not delete the state, but I removed the state frames.
In the same operation, when I finished object B, I also completed the object C, object D, object E ...
Then, BUG suddenly appeared. Every object in one or two animation becomes disorder and confusion which adds many new frame.
I guess this "Copy Objects" operation resulting the BUG.
I came here for help, because this BUG has appeared many times .
I had to repeat organize my animation.
Because I do not know the cause, I am also worried about the error appears again
This is really killing me.