You have stated the candidate no longer lives in the Parish, do they live within 3 miles of the Parish council border? (Not 3 miles from the village centre).
If you are concerned you can contact your county council electoral services department and ask them, they will be able to tell you which criteria they have declared:
They have lived in the Parish for 12 months
They have work within the Parish for 12 months
They have have an interest in a property (landlord or farmer etc) within the parish for 12 months
They have lived within 3 miles of the boundary of the parish for the previous 12 months.
Firstly: You can mix and match categories, but the dates must be contiguous, e.g. live in the parish and then move house within 3 miles limit.
Secondly: being a parish Councillor can count as work within the Parish (there was some guidance about this), and so they can claim this basis for eligibility working in the parish.