Check this old article out. I think it's plausibly related to the price action in the last few days.
Quote: This also infers that, technically, exchanges today are thinly traded. If I wanted to buy $50m in Bitcoin, what would prevent me from shorting the market by with $2–5m, forcing the price down and then buying $50m in volume from OTC traders who have clients panicking? Market manipulation, although seemingly unlikely, is entirely plausible in a thinly traded market where large trades happen outside the exchange. https://vinnylingham.com/the-1-dont-use-bitcoin-exchanges-ff019774d886