Contradiction Area #1:
We don't know what incarnation of the Master's original 12-shot regeneration cycle the Delgado Master was. In The Deadly Assassin, we are introduced to a skeletal “Crispy Master” played by Peter Pratt, and who was later redesigned and recast as Geoffrey Beevers, though it's usually understood that Beevers and Pratt are playing the same guy.
Question: did Delgado's Master decay into the Pratt/Beevers Master, or was there a regeneration in-between that existed as its own thing for a while before turning into a spooky scary skeleton?
The comic story Doorway to Hell shows Delgado beginning to regenerate, though it doesn't show into who. The Big Finish audio The Two Masters shows the Master being burnt into the Pratt Crispy Master by his future self, and what's more, it's clearly shown that the Master who gets burned isn't Delgado, but a different incarnation already played by Beevers. Ergo Delgado is either the Twelfth Master or earlier, while the Crispy Masters are various stages of decay of the Thirteenth Master.
On the other hand, the Eighth Doctor Adventures novels, in Legacy of the Daleks, show the Master being burned into the Pratt Crispy Master in completely different circumstances not involving his future self but rather Susan Foreman. And that Master is not a non-Delgado Thirteenth Master, but rather Delgado himself. One might think this means the novel says that Delgado is the Thirteenth Master, but that's not actually the case, as a line mentions that the injury is such that "no regeneration" would save him from it, allowing that he still could be the Twelfth Master or earlier.
Ergo: are the Crispy Masters a decayed form of the Delgado Master (with there not actually being a "proper" Thirteenth Master?), or of a Thirteenth Master into whom Delgado regenerated long before coming to Tersurus?