[Christoph]

Hallo henrythomas,
welcome in the Forum.

I could offer my always used recommendation close up CD/DVD-player problems.
Try to clean the lens, if you feel familiarily.
Clean the lens with a cotton bud slightly wetted with alkohol (nothing else!) circularly form the center to the edge, then remove residual fibres.
Clean also the fixture/leadings of the lense and grease them gently with white-oil or vaseline.

I wish you success!