Now in my case it is specifically about feeding, but I image other might have other issues with butlers "caring" for sim kids, so I wanted to leave the bug report open for more "info on butler behaviour" that cause issues with kids care.
I understand the idea behind butlers not being perfect, just like staff at a retail store or restaurant even though it can be frustrating, but I've had butlers not feeding babies or infants so they get taken away.
They block my sims from feeding babies/ infants because they are standing in front of the crib or holding them. And they do every interaction except feeding them. So all other needs for the child can be green, but the hunger is deep red.
I wanted to just not play with the babies/ infants in one of my saves and I wanted to see if I can spend simoleons having someone else doing (all of) it for me, so I hired a butler and and let her care for them.
When I noticed I got "will get taken away" notifications I would lock the door for to the kid room and cared for them myself. When I got tired of that I saved the game and unlocked it for the butler to see if they for once would feed them now.
And like I mentioned, I lost the kids. I quit without saving and then fired the butler, but I just want to illustrate that the butler never fed any of the kids my sims had. Even though kid care was their only thing to do for a long time (so they had time to care for themselves and sleep etc), and I even had a single baby or infant/ toddler most of the time. So it wasn't like they had several.
I can also mentioned that I though maybe this is an issue with just this one butler, so I hired another after firing the first, but it was the same thing, she also didn't feed them.
I play on pc with no cc or mods