I would concur that logic dictates that councillors automatically resign for an election hence their requirement of signing letters of acceptance before becoming the elected councillor again. This period of not being a councillor ( however short ) forms a break of tenure and as such must re-set the clock to commence from the moment they sign up again.( e.g. take their place on the council). Again, this reinforces the need to keep accurate attendance records.
Also surely this councillor should be encouraged to self question their motives for being on the council in the first place