JX-8P weird note

HI everyone,
I have a Roland JX-8P that is acting up more often. When I play in poly or unison mode there is always one key whose pitch sounds like it’s being modulated by a fairly fast LFO. All the other notes sound like they should in current patch, but as I go down the keybed, the bad key eventually shows up again. I’ve tracked it down to Osc 2 just by setting Osc 1 mixer all the way down. It becomes more obvious that something is wrong when detuning Osc 2. However even with Osc 1 mix all the way down, when I detune Osc 1 I can hear it affecting Osc 2.

Any thoughts as to what the guilty party is? Maybe something with a voice chip or the cross mod since Osc 1 seems to affect Osc 2 (since they are supposed to be independent of each other)?

Thanks in advance!


shot a video of my problem.
Hopefully, y’all can see it?