[Carrier: UPS ] UPS is unavailable because your shipment exceeds the maximum number of boxes that the Amazon partnered carrier can accept

We are creating a NON-PARTNERED CARRIER (use your own carrier) option to send a shipment however we get the above error which makes no sense.

We called our fba rep,. filed cases etc etc and just get the standard reply re-create shipment. There is a lot of repacking / effort goes into creating this shipment and quite frustrating. This looks like an obvious bug on AMAZON side but as always the sellers on amazon are the ones left holding the bag for everything.