Technics SL PS 770A Random crackling issue

Good Morning guys! A warm hello from Italy!

I'm the owner of a Technics SL PS770A Cd Player coming from the 90's. It's a perfect player to me and it works still perfectly as far the mechanics is concerned.

The issue is a crackling/distorted signal coming out especially from the right channel which happens randomly with a frequency of 1-2/10, both with CD-R or Original CDs.

The issue is not related to the amplifier since with other sources the signal is clear.

Any idea about the supposed reason of this issue?

Many thanks.