ReserveTicketsSpecifiedSeats and orphan seats

We've just started offering wheelchair/companion seating online (just under the wire...) and my solution to providing accessible seating on our "Best Seat" selection interface is to actually use ReserveTicketsSpecifiedSeats behind the scenes to gather up the available accessible seating.  The problem that has cropped up is this: say I have a row that is sold out except for the wheelchair space (A1) and the companion seat (A3), where A1 is naturally an aisle seat.  If the customer just wants a single wheelchair space with no other seating, and I plug in a request to ReserveTicketsSpecifiedSeats, it spits out a Seat Server exception (not mentioned in the API documentation) because I'm leaving an "orphan" seat between the wheelchair space and the remaining sold out row.

This is particularly irksome to me, because if I do this through our Select Your Own Seat flash app, it cheerfully reserves the seat for me.  So far as I can tell, both use the same API call (they must) with the same parameters.  Now, I don't really know much about what goes on inside our flash app -- it's a black box to me.  I do know that it doesn't connect directly to the API server (flash security wouldn't allow it, I presume), so instead it connects to a "dummy" API server that runs in the same directory: basically a .asmx file that is sort of a pass-through to the actual API server.  That file hasn't been updated in years, so maybe its doing something subtly different, but if so, what?  I can't see anything different when I run a trace: for the SYOS app WP_RESERVE_SEAT runs normally, when I invoke it from the API server directly or through my code, it never gets that far, the Seat Server barfs on the request first (not sure how that happens).

I get the feeling there's something about the seat reservation process I don't understand.