Build 4.5.0.7 of xlsgen fixes a default setting for formulas in calculations. The setting is now defaulting to recalc on open, which makes sure that when generated files are eventually opened in Excel, Excel checks whether values resulting from formulas are up-to-date.

It was 2 years it wasn't the case anymore, and a client application could have defaulting to this by changing the setting in workbook.CalculationOptions.AutoRecalc.