So, it's not really a problem, per se, and I've no idea if this is related to Patch 1.55 or if my doll was weirdly glitched.
I started a second Immortal Dynasty file (only into Generation 2). I did move in a helper family with my founder, the wife was already pregnant. So their daughter Fran gets an IF, whom I named Jaime. When Fran aged up to YA, I kept the doll in her personal inventory. Randomly one day, there is a non-doll Sim named Jaime doing the funny doll-walk through the house, and is visible to everyone. So I yank the doll out of Fran's inventory, but the doll stays in inert doll form on the floor, while Jaime doll-struts around as a non-doll.
Just to make sure Gen2 (Kate) didn't have the same weird doll thing, I take her doll (Drake) and toss him on the floor. He's a normal doll.
When Fran and Kate go to bed, Drake does the happy "Whee!" and reverts to inert form. Jaime just disappears. So I wake Fran up, and the inert doll Jaime functions properly. When she goes back to bed, Jaime does the happy "Whee!" and reverts to inert form.
Fixed, right?
Well, Kate just aged up YA. This time, to prevent any weird doll aging glitch, I removed Drake from her inventory. For the heck of it, I pulled Jaime out too (and of course, they both teleported off the roof). Drake aged up. Jaime...wandered around in doll form, then I got the notice that he has to leave soon, as he needs to be somewhere else. Then he says bye, and struts out the front door...into a Tofunda Wagon...and goes to the Bistro.
I haven't continued yet to see if he ever comes back, but has anyone ever had a runaway doll?
Fran didn't complete the Imaginary Friend opp (nor did Kate). No potions to turn them real. But Drake is still here, and Jaime just fled.