'Saving error' message when uploading a local web scene

[AiroboticsLtd]

I am trying to create a simple app using Experience Builder in portal for ArcGIS (ArcGIS Enterprise 10.8.1). The app includes a map widget showing a local web scene, but after loading the scene, it fails to save the project and I receive 'Saving error' message.

When I load a global web scene or 2D maps there are no errors, only when I try to upload a local web scene it fails to save the project.

I also tried to use local scenes with different layers to check if there is an issue with one of the layers that causes this error in EXB, bit it always fails to save.

Any suggestions? 

[TonghuiMing]

Tested on a 10.8.1 portal, it works fine:

Probably a portal-specific or data-specific issue. You could reach out to Esri Support to build a reproducible case. Thanks.