Ultra thin skin of cured resin found floating in vat, possible sources?

I’ve been repeatedly finding small fragments of extremely thin cured resin floating in the vat of my elegoo saturn resin printer.

They’re maybe a couple of CM across and so thin that I can’t measure them. Thinner than the thinnest Suran wrap by at least half. They’re very delicate and flexible so they haven’t caused any damage, but I don’t know where they are coming from.

I’ve cleaned my vat between each print, and used new resin, but it’s happened 3 time now so it looks like it’s being generated when I do a print run rather than coming from an old bottle.

Is this a known issue?