Electrostar Faulty Selective Door Opening

What is it with Southern's Electrostars? They seem constantly beset with problems.

I caught one back from London Victoria to Eastbourne earlier and the doors failed at Polegate leaving us waiting again for the computers on board to be reset. The driver apologised and blamed the selective door opening for being faulty yet again.

Once the driver managed to open the doors we were able to proceed to Hampden Park. Here, despite the platform being long enough to handle 8 car trains, and the new platform extension, only the first 5 carriages of the 12 coach train can open their doors. The problem is yet again the selective door opening.

Bring back the slam doors!