Ideas
Today I told my mother Sim to have tummy time with their infant Sim, they decided to instead put the infant in the crib, and then autonomously queue up "check on infant" so they unprompted took their infant to the crib and then took the infant out of the crib.
I also had the father Sim interrupt the other infant Sim's sleep to put them on the playmat, while the infant Sim's sleep is still half full.
It's also worth noting, neither parent responded to my request to put either infant in the high chair (I know the high chair works and I know the infants can sit in it, it worked with the same infant and chair yesterday) and let their children starve. Eventually the mother Sim did autonomously feed one of her infant Sims, but only one of them. I had to cheat the other infant's hunger need away.
After both of those events and twice having each infant Sim stuck to each parent's legs, I quit the game. It is very frustrating to play with infants when your Sims keep autonomously queueing these interactions.