Unsharp mask on adjustment layer creating errors with masks underneath

Hi guys,

I have a simple comp in AE. A video layer and a matte painting on top, with the top one containing a feathered mask to show only the bottom portion.

When I put an adjustment layer on top of those and add an Unsharp Mask, AE creates a massive error that's clearly created by the mask feather as when I turn the mask off it goes away.

I've tried precomping and adding the adjustment layer in the new comp but it still happens.

Does anyone have a workaround for this?

Thanks. !