November 2020
I got this problem before uninstalling the sims 3 Metal version on Mac. I tried both fullscreen mode and windowed mode. I can use internet properly on windowed mode but it slows down to write or post anything on the web while playing in fullscreen mode. Is this only me having this issue? I prefer fullscreen mode on Mac.
November 2020
@aodoherty I take it you're minimizing the game to write? This may be a system slowdown rather than anything to do with the internet. When the game is minimized, it can (but doesn't always) cause severe system lag for a few minutes. If you're curious, test by minimizing the game while playing in windowed mode—if it's system lag, you should see the same thing when TS3 is minimized regardless of which mode you were using to play.
November 2020