Okay, via FlyerTalk forums I think this is an issue with the terms of this particular fare.. I think.

AA has these "flexible" fares which you pay a bit more for and they are then supposed to be refundable (possibly with a fee??) but they also seem to have all sorts of stipulations to them that are listed exactly nowhere while booking (blackout dates, roundtrip requirements, minimum stays, advanced purchase, etc). I am wondering if this is the issue though why they would allow a customer to select a flight that CAN NOT be booked is beyond me.

I've tried about 40 dummy booking with all different options, party size, removing the kid, trying different flights on the same day at the same fare etc just trying to narrow down the issue. This is the best I can come up with.

I'm done. I need lunch.