Frankly we're super busy with ... literally everything.. right now, hence why we haven't replied sooner.
The problem is a caching issue on our side not refreshing the banner, unfortunately there's not a solution I can give you that I'm aware of. Further, this isn't something that's going to be fixed for some time.
If there are any more updates or I'm corrected by another JMod I'll let you know. Until then I'm afraid its something you're going to have to grin and bear.