Thanks for confirming. I have created an issue ticket here:
https://github.com/EsotericSoftware/spine-runtimes/issues/1879
We will have a look at it and will let you know once we've figured it out.
This issue has just been fixed, a bugfix commit has been pushed to the 4.0-beta branch. A new 4.0-beta spine-unity unitypackage is available for download here as usual: Spine Unity Download
The commit will not be included in the 3.8 branch due to changes in behaviour which might break existing projects. Since the 4.0-beta components are not compatible with the 3.8 runtime, I have attached a zip package to the issue ticket which contains modified versions of the components that are compatible with 3.8 projects:
https://github.com/EsotericSoftware/spine-runtimes/issues/1879
Please let us know if this update resolves your issue. Thanks again for reporting!