Epitaph Map Does Not Spawn Map Boss

I have done the Epitaph map a few times, and so far as I remember, it has never correctly summoned the Map Boss, "Saphira, the Dread(?) Consort". The Centre of the Map, presumably where the Boss generates, instead uses a non-boss variant and spawns a regular rare mob.

Yep I done this map now few times and boss checkpoint appears but no boss to be found :/