This has been happening increasingly, when I have a sheets.add or sheets.delete in excel VBA. After searching and searching I finally found the official Microsoft support pa
Deleting certain objects including ActiveX objects actually changes the VB project. It took me some time to realize that the following line of code prevented the VBE from entering break mode:
Excel.ActiveSheet.DrawingObjects.Delete
If you can identify the code causing the issue, and the order of operations isn't important, move it to the end of your script.