A320 doors not closed

When I use a ramp or bridge and I ask for a push back, it works fine. But on an airport without a helper, the door on start wil open and will not closed.
I was on UUDD (Moscow) and the bridge was on the right side of the plane. The door on the left side opened. After pushback the door on the right side was closed, but not on the left side.

Henk Scheffer