OD1 and OD2 getting terrible noise and squealing when Effects loop is engaged. I tried the Boss NS-2 in the loop and it had little effect on it. Loop pedals are TC Electronic Nova Delay, TC Electronic Chorus/flanger, Boss Digital Reverb, Boss NS-2 Noise Suppressor.

Outside the loop is Tuner, Volume pedal, BBE sonic stomp, Rockett Blue note, Wah pedal

I assume its a ground issue interference but no idea how to stop it.