Error Code When Trying to Save Game

Hi all! I am desperate for help as I have tried pretty much everything I know to solve this issue, and currently, my game is unplayable. 

I keep getting an error message with the code beginning with 510 when trying to save the game. Sometimes the game will save the first or second time I try to save after closing out the game and rebooting it, but it goes right back to producing the error code after. This error code comes along with the appearance of a last exception script in my Sims 4 folder (not in the mod folder or in-game - just when I enter the Sims 4 folder on my Mac). 

The error code first appeared after working at my sim's vet clinic one day. I thought it was a mod I recently downloaded (Afterschool mod by KawaiiStacie), but deleting my mods folder did not seem to make a difference. 

I have tried: taking out my mods folder, deleting the entire Sims 4 folder from my Mac, and uninstalling and reinstalling the game software. Taking out my mods folder does not solve the issue - it continues to give me the error code when saving although no mods are present. Deleting the entire Sims 4 folder seemed to work at first until I tried to work in my sim's vet clinic. After traveling to the vet clinic, the game would not save both at the clinic and at my sim's house, so I am guessing the saving issue isn't just isolated to outside lots.

I am at my witts end with this as I can't play without being able to save. Please help!