@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:

spine-skeletonlit-urp-2d.txt
7kB

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

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

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    Harald Thank you! This is a bug fix in Android mode in the editor.

    But users with Intel UHD graphics still have this error

      @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:

      spine-skeletonlit-urp-2d.txt
      7kB

        Harald Thanks! Wauting answer from user with Intel graphics.

        Today we started porting to Playstation and got the same error in Unity Player.

        The latest fixes don't help

          @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:

          spine-skeletonlit-urp-2d.txt
          7kB

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

            Harald unfortunately, the bug remained

              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:

              spine-skeletonlit-urp-2d.txt
              7kB

                Harald without changes

                  @paulp Bad to hear, thanks for the feedback.

                  To be sure we're on the same page: Are you testing with the exact same reproduction project that you sent us last, and play this in the Unity Editor play mode with active target being Playstation 4 or Playstation 5?

                  I'm asking to be sure you're not perhaps testing a more complex scene where other shaders are used, like additive or multiply shaders instead of the URP/2D/Spine/Skeleton Lit shader.

                    @paulp One more update, could you please test this version:

                    spine-skeletonlit-urp-2d.txt
                    7kB

                      Harald I testing with the exact same reproduction project that I sent to you.
                      Thanks!

                        Harald Thanks! Everything is fine on the test stage, there are no bugs.

                        But in game we have this bug, maybe because we are also using Spine-SkeletonGraphic.shader?

                            paulp Harald Thanks! Everything is fine on the test stage, there are no bugs.

                            Do you mean that with the last shader file that I shared three postings above it changed from having the issue to not having the issue any more? Or what exactly did you mean by "Everything is fine on the test stage, there are no bugs."? Where is the bug occurring now, using which target platform, only on the device or also when in the Unity Editor play mode?

                            paulp But in game we have this bug, maybe because we are also using Spine-SkeletonGraphic.shader?

                            This would have been my best guess so far, that the problem is fixed in the one shader above, and that there are other shaders in the scene which still have the issue and make everything look incorrect.

                                  Harald This would have been my best guess so far, that the problem is fixed in the one shader above, and that there are other shaders in the scene which still have the issue and make everything look incorrect.

                                  Yes, after your edits the problem in the editor(android/ps) and on the device is fixed for Spine-SkeletonLit-URP. Also need fix for Spine-SkeletonGraphic.shader

                                  Thanks!

                                      Thanks for the additional info.

                                      paulp Yes, after your edits [..]

                                      After which edits exactly? Only with the very last version that I mentioned above? Or with an earlier one, and if so, which one? This is important to know in order to be able to fix the issue in the SkeletonGraphic shader.

                                          @paulp Unfortunately after looking at the Spine/SkeletonGraphic shader code, there is no equivalent to be fixed (there is no problematic division by texture or vertex color alpha). So I'm afraid the remaining problem must come from something else.

                                          Do you have a screenshot available which shows the remaining issue? At which location does the problem occur, what is the object at the incorrect bloom area's center, which shader is this object using?