paulp I couldn't find any problems as far as I checked the skeletons with the default shader Spine/Skeleton, but which shader are you actually using? I couldn't find out because the information is missing in the package. It would be great if you could attach a screenshot of the material settings.

@paulp In general please never send unitypackages as reproduction project. Instead always send a zip package of your project, containing the important directories Assets, Project Settings, Packages. Unnecessary generated directories like e.g. the Library directory shall be deleted and not included in the package of course.

paulp Thank you for showing us the screenshots. I tried to reproduce the problem using them as a reference, but I was unable to do so. I will email you a video showing the result of the test, so please check it out. Also, could you please create a new Unity project and see if you can reproduce the problem, and then email us that minimal project?: contact@esotericsoftware.com

@paulp Unfortunately for strange reasons, while Misaki could immediately reproduce the issue, I could not yet reproduce it on my machine using either Unity 2022.3.18, 2022.3.35 nor the exact submitted version 2022.3.30 with Android being set as the active build target. I will get back to you as soon as I can reproduce the issue as well (hopefully tomorrow).

@paulp Unfortunately I had no luck reproducing the issue today either, neither using the Universal RP package Misaki had installed nor the original one listed in the submitted project zip file. Could you perhaps have a try whether this reproduction project also reproduces the issue on your end when updating all involved UPM packages to the latest versions of the package manager? And after that, could you have a try whether the same issue still persists with Unity 2022.3.35 and the latest packages?

paulp Harald Unity 2022.3.6, latest URP, the bug is reproduced

Thanks for checking, I assume you mean 2022.3.36 and not 2022.3.6. That's unfortunate then. It might be differences on how the graphics driver handles certain undefined cases perhaps. We will nonetheless perform some tests on our end to discover the cause of the issue, unfortunately it will likely take longer this way.

@paulp We have just pushed a bugfix commit to the 4.2 branch which should fix this issue.
EsotericSoftware/spine-runtimes2574
You could integrate the shader changes of the above commit to your 4.1 package installation. Note that the commit fixes a second files, which is an include file used by the other URP 2D shader Universal Render Pipeline/2D/Spine/Sprite.

You can also find the modified file for your 4.1 URP package below:

Please let us know if this fixes the issue for you as well.

Issue ticket URL for later reference:
EsotericSoftware/spine-runtimes2574

@paulp Oh dear, very sorry to hear that the issue still persists on Intel UHD hardware!

Could you please have a try with this modified shader version and let us know whether it resolves the issue:

@paulp That's unfortunate indeed, thanks for the feedback. We will continue our investigations.

@paulp Unfortunately so far we were out of luck reproducing the issue on our end again. Nevertheless, below you can find a slightly modified version of the shader before I'm leaving the office for today, to hopefully speed up the process a little bit:

Tomorrow I will hopefully find more time, apologies for the inconvenience!

That's unfortunate, thanks very much for the quick feedback.

@paulp Could you please try this second modified version of the shader and let us know the results: