Had a problem for the first time yesterday that my brother has been experiencing since he got the game, every now & then when going to save, the game will enter the save screen, but return quickly having not saved & nothing was able to get me off the pause menu, I had to quit out of the game & return later.
Having read through some of this thread I can see that some people are having problems after traveling & this happened to me about 30 mins (real time) after traveling back from the bar, also, when I traveled to the bar one of my sims had lost all of their emotions, anyway, the game had auto saved when I traveled back to the home lot.
I have traveled in this game before, to the park, to the nightclub, to the library & even to a public pool I created without any problems.
When I loaded the game up after the bu I was able to play it & save it all in the same slot as before with no problems, but even so, this is a really annoying problem to have hanging overhead.
ADDITIONAL: My brother is playing on a PS4 & I'm on a PS4 pro, he has less space on his hdd than I do, don't know if that helps.