Chart sheet keeps getting removed when editing a file

Hi there, I'm running into an issue which can be reproduced with this attached file: buggy.xlsm

I'm not even editing the file, all I do is load and save as such:

wb = load_workbook('buggy.xlsm', keep_vba=True)
wb.save('INTERNAL_TEST.xlsm')

And when I open the new file, I first get an error about the file being locked:

And then when I bypass, I get another alert saying that my chart sheet was removed:

Any idea why this is going on?

Thanks!