I've noticed that the grade item (and all grade information) gets deleted after the Dataform settings are edited.
I noticed after trying to enter a Grade to pass value to the Dataform. After I enter the value 1 and save the change, the grade item for the Dataform is deleted from the gradebook completely.
This makes it impossible to add a grade to pass value since that option is only available after a grade item has been created and and on editing the settings the grade item is deleted. This creates loop where you're stuck between re-creating the grade item and adding a grade to pass value.
This does not break the Dataform as the grade item can be recreated without the grade to pass value but I want the Dataform to record a Fail score on the completion progress block plugin. This won't work without a value in the grade to pass field.
Has anybody found a workaround for this problem? I've gotten the same error on Moodle 3.5 and 3.6 and on different Moodle installations.