Data entry (text) causing Excel to crash

[Chris G]

I have built an addin for my wife's workplace, with a custom ribbon tab. The addin pairs with a template for recording timesheet information.



They are running Excel 2016. (It is a version without the TEXTJOIN function, for which I have made a Function.)

THE PROBLEM: On their laptops, entering text in an information column causes Excel to crash.

Both doing Save after typing the info, or exiting the cell afterwards, initiates the closure.

The cells are formatted as General.

This behavior does not occur on either of our computers at home. One runs Microsoft 365 for enterprise. Our own PC runs Windows 2012 Home and student edition. The two versions of Excel seem to be the same.

The other difference in behavior is that while at home Excel has no issue with there being an addin installed, on their computers there is always a warning when Excel starts which says "Excel is running into problems with the [name of addin]. If this keeps happening blah blah blah."

After allowing the addin to be disabled, it always has to be reactivated from the Developer tab. Annoying.

Any solutions or clues or suggestions of things to look for would be most welcome.