When opening or creating a new Request, an exception error (ID: XXXXXX) occurs. 

This issue can occur if there is a Custom Calculation Field in the Request form which has a formula with the SUM or AVG function not in all caps.
The Sum and Average functions must be entered in all caps in the Formula window.
Example: SUM (Field 1, Field 2, Field 3) or AVG ( Field 1, Field 2, Field 3)

As an alternative, you can also replicate the SUM function by using the addition operator instead.
Example: { Field 1}+{Field 2}+{Field 3}