I cannot test on windows till Monday, but with openpyxl 3.0.0 on Linux I cannot reproduce the error - it works as expected anyway you delete the content/cell A5. Sorry... Maybe someone else would be able to replicate it. IMHO OS or excel version would not matter. Maybe openpyxl version, but both 2.6.3 and 3.0.0 work as expected.
If you can't explain it to a six year old, you don't understand it yourself, Albert Einstein
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs
How to Ask Questions The Smart Way: link and another link
Create MCV example
Debug small programs