Ahh it's kicking some legs into higher fare classes. This may be because the partner segments aren't returning real time inventory to Delta until you try and book which then proceeds to break the fare.
There are a number of threads on this, although not necessarily specifically with so many partners involved:
DL Price changing on payment attempt
http://www.flyertalk.com/forum/delta...ange-page.html
http://www.flyertalk.com/forum/delta...-checkout.html
http://www.flyertalk.com/forum/delta...it-switch.html
The most common advice is to either book through an OTA which likely won't work here due to complexity or to call Delta. A phone agent may be able to book it, but calling may also kill the deal. Although with how openly it has been discussed here, I think it will be fixed shortly anyway. It would be a pretty fun call to tell the agent each of the 13 segments and hear them price it out
