Steps to replicate:
1) Go to
https://paramquery.com/pro/demos2) Click "Tabbed spreadsheet" demo
3) Click "+" to add a new tab
4) In the first tab (PQ Invoice) add a formula that references the new tab, like in cell A11 enter "=sheet1!a1"
5) Rename the new tab to include a caret "^" and/or a plus "+"
6) In the first tab (PQ Invoice) enter a formula, like in cell A12 enter "=c3"
The formula entered in step 4 that references the new tab breaks after step 6. This only happens if the new tab has a caret or plus.
Bonus issue: Change a tab's name so that it contains a double quote ("). Then try to edit the tab name. Any characters after the double quote disappear.