Hi,
I have just encountered this bug. If you add a new image to a bone that has been flipped on the X axis, the new image will appear to have been flipped as if the bone has been flipped on the Y axis. (this does not occur the other way around)
Forgive the programmer art
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Here I have added an image to a non flipped bone
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Here is the same image and bone, only the bone has been X flipped
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Now I have added a new image to the bone, but it has been flipped on the wrong axis
I Meant to post this in bug forum, sorry.