Cannot update new calculation formula for Form Calculation Widget

Every time i try to change the formula in form calculation widget, it does not update the new formula. Even tough I clicked save, and wait for the saving to complete, and I reenter the widget the formula still remain in the old formula.

I cloned your form to test it and was able to update the calculation field without issue:

Updates made to the calculation were shown in the live form as soon as they were saved.

I cleared your forms cache in case it was a caching issue.  If you are still unable to update your calculation, let us know and we will take another look.