Only have 1 of these units on my route. Been running trouble free for about a year now. 3 days ago unit was out of service with a DTO fault only. Door open protection fault. Thought it was not seeing the open limit.went over doors mechanically and cleaned all car and hall door sills. Everything seems good. Cleared ram of the fault. Ran car for an hour with no issues. Next morning same fault. Cleared fault and car ran all day no issues. Next morning same fault. No one uses elevator at night in this building other than the cleaner. Is there something I’m missing here? Is there a certain way to reset a fault on an Otis 211?