Bingo!! I have reached out to their customer service via Twitter, and have started a conversation with someone to try and figure this out. (I'm a former programmer who used to develop & troubleshoot interface files for a commercial payroll system and various 3rd party vendors...based on what I know it does look like a failure to properly uniquely identify multiple 1099-R forms in the transmitted file, OR failure on the receiving end to recognize that the forms are indeed different).
