Simple explanation really. Swartz is selling all he can whenever he can without disrupting the SP too much. Needless to say, it's tanked quite a bit over time. He's converting warrants and selling them.
On a PR day, we get relatively high volume and "huge" selling against the buyers. On low volume days, we get little buying with little selling to offset.
Don't let anyone tell you how many warrants are left, no one really knows for sure. Prior to the last 10Q posters were stating that they were all converted and of course they were not. Now posters are stating that there are 10 million left - they actually don't know for sure. We do know that there are 18 million warrants left at the most or less.
Unfortunately retail investors and traders have caught on to this and are treating Patriot like the plague - and with good reason.
You should always expect massive selling with this stock - it's going to take a (long) while to get this moving up again.