Oooops -- I just hit refresh on EF and AC445-AC31 went P0! I guess you need to be quick with these things. How do you feel about connecting in YVR? That's still P3 (assuming that's why the change is pricing so high). All the other connections have lots of Z availability, except for AC449-AC31 which is Z0 P0 but has D3.

As a couple people further up said previously, definitely worth looking at the original fare conditions to see if it's something else causing such an expensive fare difference, too.