The following -ETER and -ELER verbs behave differently: they always and ONLY take the accent è on the first -e (-eter/-eler):
-ELER: agneler - celer - receler - ciseler - démanteler - écarteler - s'encasteler - geler (and derivatives: dégeler, congeler, surgeler) - marteler - modeler - peler
-ETER: acheter (and derivatives:racheter) - bégueter - corseter - crocheter - fileter - fureter - haleter
