Being an adjuster for Montgomery and Kone for 26 years I can tell you this, the 21 fault is a safety string error. The 65 error is that K442 on the ADON board failed to pick. My guess is that the unit has a version 1 ADON, these were prone to be temperature sensitive. Hence the change in the board design and type of components used. Another cause for this I have seen is a loose connection in the machine room inspection station or its connections to the ADON.
I'm sure there are more errors in the system. Does the building manager have any type of service contract?
