Distributed Collaboration does not sync item thumbnails

[KamilNovák]

Hello,

we have set up one-way distributed collaboration form Portal to ArcGIS Online. Everything si OK, but item thumbnail is not sync correctly. When we set thumbnail on Portal item, then item on ArcGIS Online gets empty thumbnail.

Is there some solution for this behavior?

ArcGIS Enterprise 10.9.1

Thanks

[ColeRosner]

I am experiencing the same issue with our ArcGIS Enterprise Portal to ArcGIS Online distributed collaboration. We are finding that the thumbnails only make it onto ArcGIS Online some of the time. Especially difficult for document links, which I've found will carry the thumbnail through the collaboration more often when changed in the metadata for that document link. But even then it's still only some of the time. 

We are also using ArcGIS Enterprise 10.9.1. Hope there is a solution soon.