Errors Collecting Prizes after Coop Challenge

vtkady (US1)

Each time that a coop challenge ends, I get the inevitable error below while selecting from the prize choices.  Once I get this error, there is no way to get off from that error screen other than to logout and back in.  When I do log back in, I never know if I've properly received all of the prizes from the challenge, because no other items pop up for selection after this occurs.  This happens EVERY time that coopcha ends, without exception, and is extremely annoying.  Am I missing prizes because of this, AND can it please be fixed????