After several trips the elevator loses information about the platform and the screen writes "No platform has been found".

And seems like it's client issue, because after reconnect everything ok.

MC 1.18

Video with better explanation: https://www.youtube.com/watch?v=KNnTfmCR_F4

Had a similar sort of issue although both elevators had completely forgot that they had been linked to elevator buttons as well as the lift detectors.