Renaming a sheet named "Sheet1" to "Sheet 1", should update formulas references to it to 'Sheet 1!' (notice single quotes), which it does not. The formula =SUM(Sheet1!A2:C2) changes to the invalid expression =SUM(Sheet 1!A2:C2). This breaks formulas referencing that sheet.
Iterate all cells with formulas in the workbook and add single quotes to the beginning and end of sheet name reference. The attached project changes the name of Sheet1 and then fixes all formula references to it by enclosing its name in single quotes.