Reading the 'original' Class 777 thread, and comment was made about the doors and until today never given it a thought! However, after some photography at Hunts Cross Station, I boarded a train for Liverpool Central to record a Class 777 at the station (a requested image). In the 30 minutes I was there, two Class 777's appeared namely 777004 (Kirkby line) and 008 (Ormskirk line). As an observation, what amazed me after passengers got off and on the Units at different door openings was the amount of times different doors shut, opened, shut, opened etc with the first thing that sprang to mind, if the doors continue to go at that rate, it won't too long for the door mechanism's will need replacing!
As others have suggested, other Stadler Units have a similar system and indications suggesting the doors are robust and reliable. OK it is early days but time will tell if this is a short term 'operational' issue but I wonder if the timing of the doors need to be re-adjusted? As I've stated just a casual observation.