Some people using Mods and Custom Content on the Mac version of The Sims 4 have experienced problems. Below is a summary of the issues we are aware of:
ISSUE 1: Use of Script Mods will cause the game to crash on boot on Mac. This is fixed in patch 126.96.36.1990. released Feb 20, 2015.
ISSUE 2: Some Custom Content will crash when selecting it in Create A Sim on Mac. This is fixed in patch 188.8.131.520. released Feb 20, 2015. Since there is so much custom content available, we cannot say for certain that the patch will fix *every* instance of this type of crash, but we expect it will correct a significant majority of them.
ISSUE 3: A fix for this issue was released 5/4/2015 in patch 184.108.40.2060. With this patch the OS file limit no longer limits the amount of Mods and CC that can be installed.
The game is unstable, or the game fails to start with the following error when custom content is installed: “Unable to Start. Initialization error at startup.” This is related to an open file count limit setting in OS X and is more likely to occur when many custom content files are installed.
An improvement for this issue was released 3/10/2015 in patch 220.127.116.110. With this patch we now recommend not having more than 1000 package files in your Mod directory or else you risk game stability issues. We are investigating a further fix to eliminate this limit, no eta on that fix at this time.
Alternately, if you want to have more than 1000 package files, you can use the below workaround which will change the OS file limit for all applications and will correct the issue. However this solution can cause system instability if applied incorrectly or in some special cases (see “Important Notes” below) so use at your own risk. It is recommended that you close all applications before applying the fix for the first time in case you do experience problems. Once again use at your own risk! Step 1: Open a terminal window. The terminal application can be found by doing a spotlight search for “terminal”.
Step 2: Type the following command in the terminal depending on your OSX version (Note that the commands are case sensitive): On OSX 10.10
sudo launchctl limit maxfiles unlimited
<You will be asked to enter system administrator's password to complete the command>
On OSX 10.7, 10.8, 10.9
launchctl limit maxfiles 10240 10240
Step 3: Run The Sims 4
* These steps will need to be performed every time you reboot your Mac prior to launching The Sims 4. If you fail to do so, the problem will return.
* In the case of 10.7, 10.8 and 10.9 there is an explicit number specified on the command (10240) this is the default maximum value allowed by OSX, but if your system has been configured with a larger setting then you will experience system instability and probably your machine will require a hard reboot.
ISSUE 4: Custom Content placed within subdirectories of the Mods directory not appearing in game for some people on Mac. This is due to the contents of the "Mods" folder being copied directly over from the PC. If you copied your Mods folder over from the PC, delete the file "Documents->Electronic Arts->The Sims 4->Mods->Resource.cfg" and the game will regenerate it in proper Mac format on next launch. One caveat: if you have manually edited this file on the PC then you will probably want to manually convert that file to Mac format by changing backslashes in directory paths to forward slashes in a text editor.
Note all of these issues are Mac specific, and do not occur on the PC.
Thanks for everyone on the forums that reported and helped diagnose issues, that helped immensely in tracking down these issues.