Oscillation from 2 head rig

[WORMDIRT]

So I'm running 2 heads into a single stereo cab and I'm getting crazy oscillation
I tried using a stereo pedal, Daisy chaining from the inputs different cables all the usual suspects. I've done many multiple head rigs and have never had the problem. What gives?
I figured you guys have the most multi-head rigs per capita haha and might have some insight

[whoismarykelly]

Is it a sealed cabinet? I would not run separate heads into a single cabinet. Phase issues can wreak havok.

[WORMDIRT]

It is a sealed cab.
It squeals as I turn up the volume, even with a tuner on.
I'm not too stressed about phase, I can whip up a box to reverse the phase no problem

[crochambeau]

Are you absolutely certain the two halves of the cabinet are electrically isolated?

I trust each amp on its own behaves okay on a similar load isolated from others. It sounds like the oscillation occurs when no signal is at input?

Does the oscillation occur when nothing is plugged into the input?

[WORMDIRT]

Are you absolutely certain the two halves of the cabinet are electrically isolated?

I trust each amp on its own behaves okay on a similar load isolated from others. It sounds like the oscillation occurs when no signal is at input?

Does the oscillation occur when nothing is plugged into the input?

Damn that's a good point. Both jacks ground to the plate they're mounted to. I bet plastic jacks would 100% solve the issue.
They play nice until I plug a cable in and are fine on their own.