My freeze pedal does the same thing whenever it’s daisy-chained on my 9 spot. It doesn’t do it when it’s the only pedal on it, but as soon as you add another pedal it starts to squeal. It even does it on my pedal power 2 – so I don’t think it has to do with milliamps, polarity or anything like that. It appears that it has to be isolated (even though the pedal power 2 outlets are supposed to be “isolated”).

weird glitch that should be fixed to make it truly pedal board friendly.