Googlesheets “unresolved sheet name” error – looking for deleted tab, and can’t find it even if it’s remade

I was checking some calculations, and to do it made a copy of a referenced tab. I only changed the original tab, but for some reason one of the other cells is looking for the copy.

I am in Tab 4. The error when I hover over the cell is “unresolved sheet name ‘Copy of Tab 4′” and the contents are as below

=sumif(O:O,"group1",L:L)+sumif('Tab1'!O:O,"group1",'Tab1'!L:L)+sumif('Tab2'!O:O,"group1",'Tab2'!L:L)+sumif('Tab3'!P:P,"group1",'Tab3'!M:M) 

Notes:

  • That cell should not be referencing a copy of itself. Even when I copied the tab I never made any equations which referenced the tab copy. I actually didn’t mess with that bit at all.
  • the calculation in the cell has no references to Tab 4
  • duplicating the tab, so that there is another tab named “Copy of tab 4” doesn’t fix anything
  • replacing the entry in the cell fixes the associated broken references, showing it is this cell which is the source of the issue

I am very confused! All advice welcome

EDIT: I cant seem to make any formulas now… sumifs referencing cells within this same tab still display this reference error. If I rename the tab as Copy this still happens.

I have even made a whole new tab called Tab 4, copied everything in and it still happens…