So the text of Disciples of the True Dracopheonix  says this

"You can target 3 "True Draco" and/or "True King" cards in your Graveyard; shuffle them into the Deck, then draw 1 card. During your Main Phase, you can: Immediately after this effect resolves, Tribute Summon (but not Set) 1 "True Draco" or "True King" monster. If this card is sent from the Spell & Trap Zone to the Graveyard: You can target 1 Spell/Trap Card on the field; destroy it. You can only use each effect of "Disciples of the True Dracophoenix" once per turn."

It's my understanding that the phrase "and/or" means that if I have "Apocalypse of the true Dracos ," "Succession of the True Dracos ," and "Revival of the True King " I should be able to shuffle all three of them back at once for the effect.
This effect does work in the AI mode but for some reason not in the Checkmate server.
It appears to me that True King cards are currently not considered available targets at all, but it may also be that the effect is being applied as "or" only, by that I mean that the effect may only allow you to shuffle three True King cards "or" (not and) three True Draco cards. In either instance I believe the effect is being applied incorrectly and that it should be able to target any combination of True King and True Draco cards simultaneously.

I forgot to save the replay but I will try to recreate the scenario, although I don't know how much it will help because the replay won't show my targeting screen when I activate an effect and it won't show an inability to activate an effect either.

Please fix, and thanks for the program you guys rock