I've seen some old, poser11-generated scenes loading and rapidly crashing poser12, have you tried to import one of those old scenes, instead of opening it directly?
If it works, save it immediately under a new name.

Sometime, deleting unwanted items from a poser11 file in poser12 can crash it, especially if there is some parenting plus not visible objects.

𝒫𝒽𝓎𝓁

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