Static On Phones

[Synthless13]

Hi everyone, I purchased a second-hand Roland JD-Xi recently (the red one) it seems to come from the factory with the latest firmware. This synth is fantastic and at the threat of being sacrilegious is quite a bit more fun than my OP-1 to use. I did run into something fairly quickly though... Day 1 I used for hours with headphones and had no issues, sounded great, when I pulled it out a few days later I started picking up static / cracking on key press, switched phones, same thing. I hooked into the standard outputs with phones and it sounds great. I am wondering if anyone else has seen this on the phones jack?

Thanks!