I am having problems purchasing tickets for a fare I found on ITA. I get the following American Airlines itinerary after doing a multi-city search:

7/27 AAA-BBB (connection)
7/27 BBB-CCC (redeye, connection)
7/28 CCC-DDD

7/30 DDD-EEE (connection)
7/30 EEE-FFF (connection)
7/30 FFF-AAA

All connections are under 4 hours, my routing appears to be valid. I am being vague on the exact cities because there seems to be limited availability for the fare I want and I don't want someone to play around with the specific itinerary and take away the seat.

ITA prices this out with a W fare code from AAA-DDD and S fare code from DDD-AAA. Same with AA.com. However, when I try to book, AA.com complains the fare goes up (or back down) and I get stuck in some sort of endless loop where the fare keeps changing and I'm unable to book.

If I search on ITA using the roundtrip form instead of multicity, and select the exact same flights, it prices out at the L fare outbound and W fare return. When I speak to an AA.com representative, the lowest price they could book involved a W fare on the outbound and V fare on the return, which is $75 more than the lowest price on ITA. I suspect that at AA, they are checking inventory is based on the whole outbound and similarly, return trips at one time (AAA-BBB-CCC-DDD), instead of checking availability for segments individually (AAA-BBB BBB-CCC CCC-DDD).

Will a savvy agent (any agent, not limited to AA) be able to construct this routing for me and obtain it at the lower price? Or is selecting inventory by segment somehow prohibited by the booking tools? I've already tried Orbitz, Expedia, Travelocity, CheapTickets, but have not had any luck.