A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
For anyone interested, I've posted a workaround and my findings on page 8 (https://answers.microsoft.com/en-us/msoffice/forum/all/excel-skips-to-another-workbook-for-no-apparent/272ccfbf-5aca-43f4-8e8f-c55a38043a0e?page=8)
TLDR: Follow the steps on this link: https://support.microsoft.com/en-us/help/3165211/how-to-force-excel-to-open-in-a-new-instance-by-default