This was an intentional change, all age spans were changed slightly.
I also have this problem in my game, however I don't have the problem with life stage reset to the beginning. I only play on normal lifespan with some cc. I do rotational play and keep tab of all my sims' ages on a spreadsheet. I test loaded a few households with different life stages, only the teen and adult sims have extra days added to their lifespan. For example, in the Lothario family, my teen was supposed to have 9 days before aging up to young adult, now he has 16 days left (with 7 days added). My adult was supposed to have 22 days before aging to elder, now she has 31 days left (with 9 days added). The extra days seem to be correlated to the exact number of days added to these life stages (7 days for teen and 9 days for adult). Hope my explanation makes sense.
