Thank you for sharing detailed information about what's going on with your QuickBooks Desktop for Mac. It would be my pleasure to help you get to the bottom of this strange behavior.
Based on the information you've shared above, there's a possibility you have damaged company file. You can perform some basic troubleshooting to fix these issues.
Please run the Verify and Rebuild Data feature to suspect any data issues happening with your company file. After doing so, we'll proceed with re-sorting the lists to get your records back in order.
Here's how to run Verify and Rebuild Data:
For re-sorting lists, you can follow the detailed steps in the article I'm adding below (scroll down to Additional data damage troubleshooting for Mac):
Feel free to perform the remaining troubleshooting from the article if necessary. I'm looking forward to your response regarding the troubleshooting results. Take care.