edited -- if my time&sale is accurate, 1.58$ was printed for few seconds, with just 500 shares executed at that price.
I just checked the trading prices on Monday, a total of only 24,900 shares were traded after dropping below 1.70$ in both ways, ie down from 1.70 to 1.58 and back up to 1.69...such a small volume causing this huge drop, whilst on the other hand it needs a huge volume to increase pps back to normal level as before ($2.50 + level)