Pinned straw:
Could have been an ENA holder short selling to avoid depressing the price when they get PSC stock.
Actually, ENA holders doid't really have downside but since there is new stock coming on the market held by people that didn't really want PSC, there will be an overhang.
Last price of $4.43 (11th Dec) is up off the recent low of $4.30 so the selling pressure may have abated.