I am having issues saving an existing project on ArcMap 10.3. After adding another layer to the project, whenever I try to save the project, the software crashes and asks if I would like to send an error report. I have reset my application data but the error still persists and all other projects have started behaving the same way.
Look into your Computers ENvironment Path Variables and ensure that there is only 1 Python Path Variable. Sometimes multiple variables are added and it causes the software to crash.
You can delete the variable by navigating to Windows Explorer > Right-click Computer > Properties > Advanced System Settings > Environment Variables - keep a backup of the Value in a Word doc in case removing it causes other issues.