Discussion about the Korg PolySix synthesizer

Hi all.

I got a Korg MS-10, about 25-30 years old now... 
The problem is that the pitch drifts, particulary when using 
portamento. It will slide to the target note but won't play it in 
it's accurate pitch. Than when I hit the same key
again, it can than play the right pitch. It can happen also when not 
using portamento at all actually.

Is that caused by old electrolytic capacitors which should all be
changed ?