The gallery is currently crashing the game.. If it doesn't crash, it freezes and has to be force quit.
Edit: Apparently its not just the gallery. I was only able to play my game for a minute before it froze. Loaded it up again, and again, it froze after only a minute. It's just unplayable.
Edit again: I *may* have found a solution (for me anyway).
When I looked at the latest crash report for the game, there was line after line of "EAWebkit.so" preceded by numbers, like it was trying and failing to do something endlessly. So I found the Webkit folder in Sims 4 and deleted everything in it. Then I loaded up my game, made sure I was offline, all online features were disabled, and played. No crash or lag.