This error seems to be related to certain users, but not user permissions. We were able to test it with a different user account that has the same permissions, and did it from the same computer and it worked fine. If i had to wager a guess, I think that there is a certain cluster of servers that have the issue, but it is not across all of Shopify's server set. Either way - this needs to be fixed asap. Just burned a couple hours of time from our team trying to sort this out.
I have tried to put the feature image on with two different computers and it won't stay and I have no way to save it. When my boss (who has full access) does it, it works just fine. I REALLY hope this gets fixed soon as I can't do my job and it is bothersome to keep having my boss stop what she is doing to do something so simple that I should be able to do. Please look into fixing this!!!