Based on the contexts provided, it seems like your issue might be related to the physics constraints setup or the application of transformations to your skeleton in Unity. The problem with hair physics moving in the opposite direction of movement, especially when moving to the left, could be due to several factors including the setup of your physics constraints, the way transformations are applied to the skeleton, or potentially issues with the spine-unity runtime version you are using.

First, ensure that your Spine and spine-unity runtime versions are fully up to date, as mentioned in the context about updating the spine-unity package to resolve issues (context). Sometimes, issues are fixed in newer versions of the runtime.

Second, consider the advice given in the context about physics causing animation loop breakage (context), which suggests looking into how physics constraints are set up and interact with animations. Although your issue isn't about animation looping, the setup and behavior of physics constraints could similarly affect how hair physics behave during movement.

Third, review the setup of your IK bones and constraints, as improper configuration can lead to unexpected behavior, especially when flipping or moving in certain directions (context).

Lastly, if none of these suggestions resolve your issue, consider reaching out with a detailed description of your setup, including how you've configured your physics and any relevant constraints. While I can't directly fix the issue without more specific details, these steps should guide you towards identifying and resolving the problem.

@Metaru If the above does not resolve you issue, could you please create a minimal Unity project which still shows this issue? You can send it as a zip file to contact@esotericsoftware.com, briefly mentioning this forum thread URL so that we know the context. Then we can have a look at what's going wrong.