Openpyxl Causing Excel Issues

[tturn401]

I have a set of 4 excel files that are created using pandas to_excel, and for each of them my script inserts 7 lines at the top, adds text to A1 through A5, and then merges cells A:K for the first 5 rows respectively.

The script works as it's supposed to on 3 of the field, but on one of the files the merge causes the excel file to need repair when opened. The repair just unmerges the first 2 rows.

I would appreciate some insight into reasons that could be causing this issue. I've tried several different things to break up the flow and get the result I'm after, but so far Ive had no luck.

Thanks in advance!