Sims can’t interact with infant

I am having a problem with interacting with infants too, but it's a bigger issue at hand. The infants are wandering away from the home lot by themselves. This has happened twice. I have only one infant in my game, so I could get used to them. I was playing an active family, who started crying because they received a moodlet that informed them that some random baby (that they didn't know) was taken away due to neglect. I went to the home lot in Newcrest, where the infant lived, and her thumbnail picture was faded, and there was an indication that she was in Willow Creek. I went to find her, and she was laying alone on the sidewalk. Her parents tried to pick her up, and they couldn't interact with her. 

I was able to get her home via Manage Households, and transferred her to another family (the crying family), who later adopted her. This was last week. Today, I log on and find that the infant (who now lives in San Sequoia with her adopted family) wandered off by herself while I was playing another family in another city. Come to find out, the baby somehow wandered to Del Sol Valley, and was laying on the sidewalk alone. I sent her parents to pick her up, and again, there was no way to interact. I was able to send her home this time via clicking the "home" icon on her thumbnail, and  I also sent the parents home. When their home lot in San Sequoia loaded, the mother was holding the baby. I can interact with the infant on their home lot, but when they wander off, I can't.

I am afraid that this infant is bugged, and I might age her up to a toddler and not have infants in my game. 

PS: The infant was initially adopted by the Newcrest Family via the computer. She's not a CAS or Science Baby. The San Sequoia Family formally adopted her after I transferred her to the home via Manage Households. Everything was fine, as I was playing this family, until I started playing another family, who incidentally live in Del Sol Valley. It's odd that the baby wandered to Del Sol Valley, where the other family lived.

The Last Exception was as follows: 

Mod Path Module Function Line Error Class

@kaitoujeanne01 Would you mind sending me your save ? Instructions in my signature

Please let me know which family has the issue.

ok this is interesting and I've been searching for infant issues to help with everything going wrong and this thread really hits the nail on the head.
I have one main save and one infant was found outside their house quite a long walk away.  I was so confused how it even got there.

My main sim family has infant twins (nightmare) and at first they got milestones, the early ones, no problem.  I had all the other glitches like getting stuck on the feet and the parents pick them up and set them down over and over never actually completing the other stuff (like diaper change or feeding/putting to bed).

I have been troubleshooting this for a million years it feels like.  I've had issues since the launch back in april.  

Now none of the infants will complete the later milestones like crawling/standing/finger foods.

I have aging paused and keep trying the interactions but the milestones don't work anymore for some reason.

I have moved them into a new home altogether to see if the home is glitched.

BUT!  The posture errors, holy cow.  There are so many of those.  I've been reading about them and I've tried all the suggestions but nothing works and when I get one, I get like 6 or 8 pop up notifications that it's ignorable but it happens over and over.  

I have tried with and without mods and even tried with one mod at a time to see if there is a mod (I don't use very many) triggering the issue.  It happens all of the time.

I actually get so frustrated that I shut the game off and do something else.