Philips cd960 problem

[muizel]

Dear sirs,

Maybe you have an idea ? about this,
I got myself a vintage Philips cd960 and dac960 the look like new and they also sound wonderfull using the cd960 as a drive and the dac960 as converter.
But on some cd's (not all) I hear through the sound some static
clikking noises (just like dust on a record) alway's at the first 4 or 5 tracks, tracks later on there is no problem.
I allready changed the laser and drive but it makes no difference. It is the CDM1 drive (very nice) by the way.
Do you have an idea ? The laser is good it even reads cdr without a problem and it is only on a few cd's that I have.
The clicking is both on the digital out via the dac and on the analog out from the player.

Any ideas would be great.

Regards René.