DATETIME_ADD error when using field as interval

[hadardo]

Hi,

I'm trying to use the DATETIME_ADD function to combine date+hour and minutes from two fields. The function itself has no error and is being parsed correctly. However, the widget is displaying a "Data Set Configuration Error". 

Any ideas? Is this a bug?

[ArkadyZagdan]

@hadardo 
It would be easier to troubleshhoot if you paste your exact formula here and elaborate mroe about the expected result.

[hadardo]

@ArkadyZagdan , like I wrote, the interval parameter is a field:

DATETIME_ADD([datetime_field], INTERVAL [field] {part})

I attached a screenshot as an example, but this is happening with every datetime field and every numeric field or numeric result of a calculation on a field that is used in the INTERVAL parameter