thanks, I would guess the markings of the close are being done by the same party as the stock moves up & down, so whether sells at the bid whilst the stock is in rally mode, or buys at the ask whilst the stock is in selloff mode, I guess same party is doing it, perhaps a MM? perhaps Shorts? perhaps it is LPC? I doubt it is Gram Gram , lol
BTW, I think there is much more serious manipulation of the stock throughout the trading day than the last minute, it should be obvious to anyone who follows trades closely