Also, the top lever does not fully centralise when the gun is closed. Is this normal?

Clay pigeon shooting
MIKE GEORGE says:
This is quite normal, and nothing to worry about.

The stiffness will disappear after a few hundred shots, as the jointing and ejector mechanism get ‘run in.’

It may take a little longer for the bolt and top lever mechanism to bed in, but eventually the top lever will centralise.