Hi, I've been having a problem with my Line 6 Spider IV 150 recently where i'm getting a lot of gritty distortion on top of my amp preset. It's very noticeable as there is also a large increase in volume and feedback. The problem will go something like this: Playing on any amp setting -> gritty distortion comes in, increases volume and increases feedback (this lasts maybe about 5 minutes but can last up to 15)->sound goes back to normal. I have already checked that my settings are correct, and have identified that there is no problem there. The problem is pretty difficult to identify as it's fairly intermittent. If anyone has any ideas as to what this could be or how I could fix it please let me know, it'd be much appreciated! Thanks.