An update earlier today caused an occasional issue with racking (when you have a mix of upper-case and lower-case container codes, which is very uncommon and slipped through the net in testing). I suspect this is what you’ve experienced here. I’m really sorry about this.
A fix for this situation has been deployed now. Can you please try again now and let us know if the issue is resolved? If you still have the tab open with the error page, you should be able to refresh it (and re-send data if prompted).