Now that the bug with the Sims randomly aging up after visiting CAS or loading the game is fixed, there’s reports that there are still Sims aging that shouldn’t. This is a one time occurrence though and doesn’t happen every time you enter Live Mode. Some people also report their Sims are being reset to the beginning of their age group.
This isn’t a new bug but more an undesired side effect of Maxis changing the length of each age group for all lifespans.
These length are now what you will get