It has been like that for over a year for BA search, and QF have a similar problem since they made some change to their awards search. Same thing for CUZ and other cities (GPS etc).
If you want to get LA seats using OW miles, you must do it 320/321 days in advance, after a day or two, they will remove their seats from the OW inventory, sometimes they put some seats back to the system.
I had problem an award few months ago, route PPT-IPC-SCL-MIA, after talking with AA, they spoke with the ticketing department for OW awards tickets, then they call LA, and magically in a minute, they opened a lot of seats for that route, it lasted over a week (7 seats available on each flight). This is a common problem for IPC-PPT-IPC, another hard to find is MIA-EZE on 4M.