Positive valued RMAs

Occasionally as circumstances would have it, an RMA is created with a positive value.  Our implementor does not know how to prevent this from happening.  It happens with some customers all the time, other customers on a seemingly random basis.
This wreaks havoc with autoinvoice.  Autoinvoice tries to process the transaction, it would appear, and is unable to do so.  The process thrashes indefinitely backing up other receivables transactions.  In order to proceed, the RMA must be deleted.

Has any one experienced and overcome this behavior?

Thanks...