I work in a mailing house in the UK. We don't print mags, we recieve them from the printers and mail them out.
The problem I'm seeing here is VERY unlikely to a mailing problem. ie it is not likely that the problem is at the sending point. If it where then the problem would spread itself a LOT thinner and the same peson would not be affected as often, UNLESS, the people being affected are near the end of the run, and they regularly don't print enough mags.
This is a problem we see often when we are not supplied with enough mags for the subs. More often than not the printers will send more mags, and we'll finish the run. BUT it has been known for the printers to inform us that there are no more to be had. This however VERY rarely happens with mags that are also available 'off the shelf' as subs are normally handled first.
I see this problem as being at some point AFTER the subs enter the postal service.
I DON'T know much about the US postal system. I know the UK system very well, but we only really have one carrier at the moment, that covers the whole of our small island.
America is a BIG country, and the mail will 'I presume' go through many hands. Every time someone new handles it the chances that a mistake will happen, or a theft will occur, is greater.
If I were Paizo, I would keep and accurate record of when and where subs copies went missing, and POSITIVELY ADVERTISE that you're doing it. Ask customers to report the problems. Look for patterns. Why should the customer have to chase through the system to find why it hasn't been delivered? That's what they pay you for.
With our single carrier system in the UK we have the ability to insert Micro Chips in with the mags, that can be traced through the system. Then you can find where the problem is, when the mag enters a sorting hall, and doesn't leave, Royal Mail can track the problem. I don't know whether that is possible in the US, but we've used it in the past.
Just my thoughts.
Soulcat