Group SP Site (Group image/logo Not Updating)

Next response, though very unsatisfactory:

I’m glad that the solution provided worked in you case as well.

Unfortunately, the root cause analysis of the issue is out of support boundaries. If you’re interested in the root cause analysis you need to open a payable ticket at https://support.microsoft.com/oas/

We can wait until tomorrow in order to see if the rest of the group’s pictures will be synchronized. In case they’ll not, I’m kindly recommending you to change manually the picture from the Site Assets library.

So the recommended workaround is to manually update the __siteIcon__.jpg in the SiteAssests library of any affected group or teamsite. 

Does anyone have Premier Support to finally get a root cause?