Excel auto-groups tabs when I try to paste special

As it says in the title. When I am trying to focus on only one tab "1" out of 15 other tabs, Excel groups all 15 tabs by itself as soon as I hit paste special. I went and de-selected the tabs and chose only one tab, but it keeps doing this.

Does anyone know how to stop this?

Can you post your file so we can take a look?

EDIT: sorry the problem has disappeared after I closed all my files, but it's really odd how earlier Excel was deciding to auto-group tabs which was very annoying..

I'm trying to create a sample for you but if I condense the file down, that problem goes away, so I don't know what's triggering this.

This file was originally created from a blank sheet so no VBA, no macros, nothing.

That is the only thing I could think of is that somehow all those tabs were grouped(selected).
Hope it is ok from now on