here anyone that have found a fix for this annoyance?

The Office Suite applications can be annoying, and especially Excel...

If you open more than 1 spreadsheet in Excel, there are 2 possible ways to do it:

1) You have 1 "instance" of Excel that has 2 spreadsheets open in it.

2) You have 2 "instances" of Excel that each have 1 spreadsheet open.

Those behave differently. You should check that.

The default is #1. You must explicitly open a second instance of Excel for #2.