Thomas -- Thanks for reporting this. If your web map is public it would be great if you could share a link to it here. If not, please contact Esri Support so they can work with you on troubleshooting this.
Owen - The map is not public yet. I've put in a bug report with ESRI support, but I figured someone might find this helpful since I could find no documentation about it (I realize there was an update yesterday, so maybe this is a very new bug).