Excel Crashing On End Sub Line?

I made an Excel/VBA solution for a company in which userforms were created and manipulated programatically, including their code modules. They would then be deleted so next time they were created there wasn't naming errors.

They acted as data input forms which would have an input control for each column of data on the sheet.

There was one method which would create the form and then call another to add code to it's code module.

In one scenario, if the user would do data entry on one sheet and then immediately after do data entry on the same sheet using the data entry forms.

When this occurred something peculiar happened, after the method which added the code to the code module executed excel would crash. By putting a MsgBox to pop up just before the End Sub statement and having another in the calling function immediately after the procedure call. It became evident that the sub adding code to the module was not exiting correctly and causing the program to crash.

In essence the program was crashing when End Sub was executed