Why PPS is weak. Here's one other possibility. When companies are knocking at your door trying to get you to take some money the pps is often moved down so that the newly issued underwriting stock price is set below the recent average market price.
Not saying this is happening. But it just happended to me with another stock I hold and is just another possibility.
I bought more at today's low and am quite happy to wait for SPM to move even lower if it means I can buy more of a stock that will eventually move back up (as long as we have full disclosure which, of course, can't be guaranteed).