Eraser Brush Auto-Applying Mask? (Designer V1)

[awakenedbyowls]

I'm rubbing out some pixels on a design and rather than just deleting the pixels it keeps applying a mask

I've tried this on a new file - lay down some pixels and rub some out and it just rubs them out without applying the mask

Why is this happening!?

[awakenedbyowls]

I think it's because I'm applying the Eraser to a Group - I've gone and ended up with a complete mess of Pixel layers that I can no longer figure out - Pixel Spaghetti !