Thanks for including the forms.
I notice the button has a SubmitToSharePointList command followed by a Delete command.
This means that if the SubmitToSharePointList command produces an error, that error will be cleared once the Delete command executes. qRules displays the Result, Error and Success for the most recent command.
Can you try using a button that only uses the SubmitToSharePointList command, and check the Error node after clicking the button? This will tell us whether the command is returning an Error.
Let us know what you find. Thanks!