The hit die advancement for the true dragons and the epic dragons have a HITDICEADVANCEMENT limit of 99, but it should be unlimited.
(Similarly, the docs give an example of the Assassin Vine of a monster limited to 99 hit die, but it also appears to be an unlimited species. If I am correct about dragons, this could also be fixed. The other two examples do not specifically name a species.
Assassin Vine: starts out as Large, with 4 HD. 5-16 it is Huge, 17-32 it is Gargantuan, 33+ it is Colossal. 99 HD is the maximum it can ever raise to.)
I could do this, if approved.
Completed: At revision: 20146