Hi Volunteer 19
The service chap has disabled relevelling. This is why when a lift halts for a long time at a floor, the piston sinks, the lift leaves the door zone and since it is out of DZ, when a call is registered, without DZ on, the door will not open on this floor.
This is why when you called the lift from the 3rd floor, the lift stopped in the DZ and the door opened. For the lift doors to open, the DZ signal must be active, and if the lift sinks it leaves the DZ hence the doors won't open as the circuit
path is broken when it is out of DZ.


When you observe this happening next time, after calling the lift from another floor and doors open, return to the floor where the door was not opening with a lobby call. If it opens, then 100% relevelling is disabled by the elevator technician. Cool ways of surreptitiously forcing you to modernize the lift.

Your lift is good.No need for upgrading.

Slap a legal case on the maintenance company or raise a complaint with the consumer protection society.