infant doesn't reach milestone

This is an old bug. My infant will achieve the milestone, have it in the queue, have a parent "see what's happening", and then never get the milestone notification or have it added to the simology menu. 
I don't know if this is also relevant, but he actually achieved some milestones and then lost them too. I definitely saved my game. 
I essentially loaded my game, noticed he didn't have all the milestones he had achieved, and then now cannot achieve any more. Really frustrating as I've tried so many things in the hopes to fix it but I can't, and I want him to have all his milestones before aging up.