Real-Time Drawing and Editing mode does not work for objects with both an effect and opacity mask added
If an object has an opacity mask, Illustrator renders it correctly when the object is moved, the mask moves together with the object.
But if you apply an effect to this object, Illustrator will keep the mask in place while the object is moved, as if it has the mask unlinked.
On the other hand, if you unlink the mask for the object without the effect and try to move it — Illustrator will render it wrong again, as if the mask is linked, until you release the object.
Please see the GIF attached and try the file yourself.
I reported a similar looking problem before, with a clipping mask applied to a layer, here: