What game length have you selected? I found having to play on Normal for the Pinstar Legacy Challenge, and sticking to the same game save for ten generations that most of my town had aged up. In fact, it was starting to grow empty. :o Now, you stated you just started a brand new save and it's still happening. That's odd. Do you have aging on or off? And is it strictly for the active lot, or for all? I would check out your settings to see if this is partially the problem. Also, mention this to the Devs. They may need to examine your game save file to figure out what's going on in your game. The other thing you might try, since you've already done the 'repair' option, is to pull your Sims 4 Game folder out and place it on your desktop. Start the game, play it to see if all is well, and then return your Tray and Saves folders, so that you have your Sims and builds.
@rosemow please list any other helps for this situation. Thank you.