A bit of experimenting and it seems that there's some code for the biconditional data that compares the two cards alphabetically, presumably to make sure that only one pair gets displayed. This code has run amok and has prevented a lot of biconditionals from being displayed. For instance, "Upgrade,Develop,Chapel,Remake,Salvager,Apprentice" as conditions will only list Upgrade/Salvager, Upgrade/Remake, Salvager/Remake, and Develop/Chapel, in that order, and no other biconditionals. It doesn't seem to matter what order the conditions are in either, many biconditionals just don't show up and the ones that do show up always have the one that is later alphabetically listed first.
I put together one of each letter to see where the problem might be: Adventurer,Bank,Chapel,Develop,Forge,Gardens,Haven,Island,Jester,King's Court,Library,Monument,Native Village,Outpost,Pawn,Quarry,Rabble,Smithy,Tunnel,Upgrade,Vault,Workshop,Young Witch
Y: WVUTSRQPONA (Where's most of the beginning of the alphabet?)
and similar until
M: LKJIHGFEDCBA (This looks good!)
and similar until
H: GFEDCA (where'd B go?)
And similar until the end.
Something screwy is happening between A and B such that A always shows up, and B doesn't for most of the alphabet. Something also is happening between N and M such that cards on different sides of the divide are only put together unless one is A. More to come....
edit: Adventurer and Alchemist appear to be the only ones that always appear. Starting from Ambassador they don't.
Bazaar through Ambassador are not showing up for Bishop forward.
Things are just really screwy; there might be a pattern in what is or isn't showing up but it's starting to get really weird as I look at more and more combinations. Ambassador shows back up on Conspirator; Apothecary and Apprentice are back on by Ghost Ship; Bank is back on by Inn.