This happens in my game too. I always thought it was a glitch. There are some wonky things with toddlers, particularly actions with toddlers. For example: If you have the changing table, after washing or changing an infant or toddler the adult sim may automatically put the kid down on the ground and THEN cancel any remaining actions in the queue. Or there is a known issue where reading your toddler to sleep distorts the toddler (stretching them) and then suddenly they are asleep.
In my game if the adults are always busy, they won't pick up the toddler. It's something they will automatically do if an adult is doing nothing and a toddler is doing nothing. If you want to prevent it, I suggest you always keep something in the queue. Unless it's happening anyway, then I don't have any tips. Are the sims canceling actions to pick up toddlers or is it only happening when they aren't doing anything?
_Slavic
