I have received the same nondescript "Staging failed" error when attempting to publish singular analysis tools, such as Clip, as well as more complex models that leverage multiple tools.
The model I am trying to publish was originally created and published as a geoprocessing service in ArcMap 10.6. I migrated to model to ArcGIS Pro 2.1.2 where I could take advantage of the new "Add Relate" tool to improve the model output. I have completely rebuilt the model in ArcGIS Pro and successfully executed it locally, but attempts to get it to publish to Portal as a Web Tool fail. I have been able to successfully publish feature services, map image services, tiled services, etc to the same Portal using ArcGIS Pro 2.1.2 and can't understand why I'm getting errors only when I attempt to publish Web Tool
My previous case relates to BUG-000111032
I'd like to know if anyone else if having trouble sharing web tools to Portal from ArcGIS Pro. Are there any Portal configurations that I may have incorrect that is preventing me from publishing Web Tools?