The behavior you're experiencing is due to changes in how Spine handles negative scaling and rotation between versions 2.1.27 and 3.0.16. In version 2.1.27, negative scaling on a parent bone would cause child bones to rotate in the opposite direction, which was a result of how transformations were calculated. However, in version 3.0.16, the handling of negative scale and rotation was updated to provide more stable and predictable results. This change means that the rotation direction now aligns with the mouse movement, even when the parent has a negative scale. This update was part of a broader effort to improve the stability and usability of transformations in Spine, as the previous behavior could lead to unexpected and unstable results.

To adapt your projects to the new version, you may need to adjust the setup of your bones and possibly use transform constraints to achieve the desired behavior. This might involve re-evaluating how negative scales are applied and ensuring that the intended rotation and scaling effects are achieved with the updated transformation logic.

mwhite Unfortunately, the process of converting a Spine skeleton created with a very old version, such as 2.1.27, to the latest version causes this to happen. Unfortunately, there is no special workaround for this, so you will have to manually modify the animation in cases like this where changes in the way the bone transform is computed or handled will cause the animation to change.

mwhite Unfortunately, we do not provide a script for this particular case, but you can write your own. If the skeleton created in 2.1.27 has not yet been exported, you can export it once in JSON format, then write your own script to process the JSON and import it into Spine. Documentation on the JSON format can be found here: https://esotericsoftware.com/spine-json-format