Volca Keys VCOs out of sync

So my Volca Keys is a couple years old now. Recently, I noticed that one of the 3 VCOs is constantly out of scale with the other 2. That means, when you play them in unison with no detune, the notes get gradually out of tune as you go along the keyboard. You can hear one VCO is almost half a semitone out at around B3; the notes are more in tune the further away from B3 you get.

The auto-tune function is also going crazy, constantly trying to fix but it can’t because one VCO is out of scale.

Anything obvious I need to look at?