I can't imagine there's much (if any) tax loss selling going on, and the short interest update to November 30th still isn't out that I can see.  

Recent spikes in the PPS have coincided with significant drops in the number of shorted shares.

• Up to June 15th the short number was over 1.6 million and the PPS around $1.70
• Up to June 30 short number down to 1.28 million and the PPS around $2.40
• By Aug 31st the short number was down to ~603K and the PPS was pushing up to near $3
• By Sept 15th the short number down to ~322K as the PPS climbed over $4 briefly

And since then, through Sept/Oct/Nov the number of shorted shares reportedly stuck around that same 320K area.

The next update, if it ever comes, is supposed to give us the number up to November 30th.  Given that the PPS has basically been stuck in the $3 to $3.30 trough (give or take) I suspect it hasn't changed much.  

The update through to December 15th should be out Wednesday/Thursday of next week, hopefully we see both a big drop in short interest, and a corresponding spike in the PPS.