.... but as I understand it, the lens was new - now 6 months old. It should just work. This is something refereed to as merchantability - its a concept in consumer law that basically says, you buy something and it should work for its stated purpose. You buy a new lens, it should focus across its designed focal length range.
Pentax should monitor the products as they flow through at CRIS for items that go through there multiple times that are new within the warranty period. Things that go back for a second time within the year should get flagged - a weekly report to the VP (the information is already in the database - just mine it, simple enough). This is the beginning of a trend analysis. If there is a bunch of XXXX (you name it) that starts to trickle in, and then some additional units, there is a manufacturing problem. If its just a single unit bouncing back - then its a lemon (or the beginning of a trend). In either case it is something that needs to be attended to both on the customer front (swap it out), and in manufacturing.
This is not a new process or a recent discovery. This is basic manufacture engineering - it goes all the way back to
Demming.
What you don't want is another 16-50 debacle that just drags on for years - essentially killing the produce in a slow death spiral. Fix the design, identify the part, the assembly process, the QA/QC - whatever the problem turns out to be.. In order to do that you need to understand, identify that you have an inherent problem(s), and identify and localize it/them. For that you need bad sample units. This is not rocket science. This is basic product management.
Right now the DA * 60-250 has a sterling reputation. This happens, and now a few folks who have just bought it or are thinking about buying it are starting to question what they should do - and should they buy it or not. Plus, its the holiday season that the majority of buying is done in. It can be a good year or a bad year based on the last 60 days. Why put all of that in jeopardy and at risk.
Cost - sure it looks like it may be an expensive proposition at first, but you fix the product - and you make it back up in sales, or kill the product so that you no longer have to support it and have it suck the life out of you if you are unwilling to fix the problem. The first unit with the problem is a lemon, the second one (depending on the amount of time since the first), may also be a lemon. Just replace them. When you start to have a number of units come in - it is a problem that needs to be recognized and attended to.
And it is just not a Pentax problem. Look at Nikon with the D600 with the oil film that turns into a dust and dirt issue. They never really did anything about it - finally a cleaning, then replaced it with the D610 which included a very small feature upgrade just to save face.
This one single thread is now 35 days old. Its the second thread on the OP's lens. This should have been addressed and fixed 30 days ago - with the OP posting images and saying how great the lens is and how Pentax did the right by him. The OP should be out with his lens this last week shooting images (or studying for midterms) - rather than waiting for a phone call from on high. Instead he is cooling his heels waiting on a call.