I need help here guys... About a month ago, I bought a used Zon Sonus Special six string. When I first tried it I heard a high pitch sort of "screaming" sound coming from the input jack when dislocating the cable slightly but I thought what the heck, it can be fixed, problaby some oxides (spelled correctly..?). But I told the seller about it, and he cleaned out the jack and everything seemed to be fine. Then maybe a week and a half after I bought it, the sound came back. And yet, if I just unplugged the cable and put it in the bass again, it disappeared. Then, for every week it got more worse. It came more frequently and was harder to get rid off. So when I had the bass at a local luthier to get me some new straplocks I told him to fix the jack. He sprayed it for oxides but a day after I got it again, the sound was back AGAIN! So I'm thinking it could be a faulty connection due to it could be a bit worned out. So I opened up the preamp compartment and tried to sort of put more "tension" on the thing that grips the cable... But I had to pull out the jack a bit to get access and one soldering fell off, even though I pulled very carefully. So I problaby have to take it to the luthier again maybe to change it, but some of you may know what to do save the jack. And just so you know, OFF COURSE I have tried it with several cables, I'm not that stupid. And about the sound... it is not super high pitch, but more like around the pitch of a guitar E-string (the high one). So... anyone had any experience on this..?