Please remove the validate rule in the Validation tab of the Flow action(in all circumstanced and base rule). Call the validate rule in the Post processing activity of the rule(in all circumstanced and base rule) by using Obj-Validate Method. after this step call the data transform.
If this checkbox is always checked before coming to this flow action, then have a pre DT in flow action to set this property to false and have a post DT in flow action to set this property back to true.
This way if validation fails then checkbox would be unchecked
This works if this property does not drive the validations in your validate rule.