[ROM] Sages are replaced by random NPCs

This happens in every single one of my saves, old and new, modded and unmodded. I just assumed it was by design as I've noticed other packs where there are NPCs with specific jobs (Cottage Living for example) will often lose those jobs within a few sims days of play, even though they are still alive (Michael Bell, the Henford Mayor and her Delivery son are the usual culprits in CL to lose their jobs quickly). 

I play on PC and am happy to share completely vanilla saves where this has occurred if needed.

Do you have Neighbourhood Stories turned on? Sometimes the game moves them into a lot and they lose their NPC role. This often happens with my Cottage Living NPCs too, they have to be "not in world" to keep their jobs

Ah, OK. I do usually have Neighbourhood Stories on in all my saves, though I'd have to double check.  I wonder if the 'not in world' rule applies to sages too.

I guess with any new saves in which I use neighbourhood stories I should go into the individual households and turn off the stories and see if they stop being sages/lose their cottage living jobs.

This happened in my game just now. My spellcaster sim has a relationship with all three sages. When I went into the magic realm to have him learn from them, Morgyn Ember was replaced by Hinata Kimura. Simeon and L. Faba are still sages. 

I'm in the same save three days later. Hinata Kimura, who replaced Moryn Ember as the sage of untamed magic has now been replaced by Kendall Crosby. Simeon and L. Faba remain unaffected. 

Has neighborhood stories has moved your replaced sages into a world somewhere? I've found that they tend to lose their roles in my game unless they stay "not in world".

As soon as they moved into a lot, the sage got replaced.