The Bing Ads Editor and Bing Ads API is having some technical difficulty around some of their extension uploads. According to the Bing status report Starting July 11th 11:07AM UTC, customers making updates or creating new Call, App, Location, Callout, or Review extensions will see an error message regarding ad scheduling at the time of doing a "Post Changes" in Bing Ads Editor or performing upload through Bulk API."
Bing said that the engineering team "has been engaged and have identified a fix for release." They added that "this issue does not impact delivery."
There is a workaround for this error, to "make updates and create new extensions within the web user interface." Nice workaround.
In any event, it seems like this should be fixed soon.
Forum discussion at Twitter.