[hypoxia]

Is it a Fantastic Vent?  While I cannot argue with any of the solutions presented and although I do not think it s the problem, there is a lid plunger switch on Fantastic Vents that does lose contact eventually which simply requires moving it around to clean off anything which may prevent a good connection.  While I do not think your problem is caused by this, it is a consideration.  In the end, I think it is a bad board on the vent and if Steve is correct, in your case, I would call Lippert, who acquired Fantastic Vent.  They seem to be fairly good in customer service.