giomode I'm afraid your question is rather vague and I'm not sure what to advise you. I assume you mean that there is a difference between the animation played in Spine editor and the exported result, but without knowing the version of Spine editor you are using, your export settings, etc., it is impossible to determine the cause of the difference. Please let us know the conditions under which you export.

By the way, if English is not your native language, please post in your native language. This forum has a translation button so we can read your post using it.

giomode From your description, it sounds like there is simply something wrong with the file management. Could you please email us your Spine project and the minimal project that can reproduce the problem (I mean the project with the Spine runtime you are using)?: contact@esotericsoftware.com
Please include the URL of this forum thread in the email so we know the context. Then we can take a look at what's wrong.

giomode Thanks for sending the skeleton data files and the Spine project files. I have seen the Spine project and I have confirmed that I can play the animation with the exported data, but I don't know the difference between your expected result and the result at runtime. Could you send us some screenshots showing the difference between the expected results and the result at runtime?

By the way, you mentioned that your project uses Pixi.js, but unfortunately when Spine 3.8.99 was released, there was no official Spine runtime for Pixi.js and only third-party runtimes were available, so if the problem you are experiencing is caused by the third-party runtime, please note that we are unable to provide support.