Lots of distortion/overdrive, especially many of such pedals switched on simultaneously, will create feedback easily. Your "Insane" effect sounds like lots of distortion to me.. I've played with EHX BigMuff (Ru) & Boss DS-2 simultaneously in the effect chain. Both on makes a lot of extra backgrond "hum" noise even with only a little bit of distortion/sustain turned on in the pedals, with higher distortion settings it's all feedback if there isn't a chord or note played.
So I guess it's because of the heavy distortion... But trying with other guitars using the same effects is a good idea. You can always use the guitar's volume pot or pedal the distortion off when you're not playing and don't want the feedback screaming.