does it do it on both vats?
Only the layers that are exposed individually, in black and white when a white layer is exposed to the resin
it hardens moves up back down and again exposes the next layer.
So does this happen on both vats and is it happening on just one print item or is it happening
If it is happening on all this would be when you submit a trouble ticket at this link or call them first https://www.b9c.com/contact/contact-us
other wise I would take a look at you file and make sure there is no strange things in it by scrolling through the slices to see if there is a flash outside the item.