Micro Korg noise on audio output

Hello,

Not easy to describe but when a note decays right at the end as the level drops, the sound is followed by a ‘crackle’. It appears to be there no matter what sound is played but it is easier to hear on certain sounds than others.

To me looks like an issue with the audio output section. Has anyone ever come across similar issues with this synth?

Cheers, Ant.