Not to rub salt into the wound, but did you happen to see this current post where somebody sent in a second-hand Sigma 100-300mm f4 for repair, and Sigma repaired it in one day, for free?
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/166251-sigma-service-rocks.html
Where does Pentax get off charging a premium for their lenses, giving them a measly 1-year warranty, and then taking forever and a day to fix them? Especially when it seems that they fail at a disproportionate rate. Why do they ever think they'll get any of my money if they don't shape up?
I already own a Sigma 50-150mm f2.8 and the 30mm 1.4, and they're both incredible lenses. And when I sent them in to Sigma recently for calibration, the turnaround time was
a matter of hours. I'm always saving up for another lens, and my money will continue to go to Sigma. The 85mm 1.4, the 8-16mm, and the 17-50mm 2.8 are all on my list. Sure, I would love to support Pentax, but I work hard for my money so I'll put it where it goes farthest.
As far as I'm concerned, Pentax should send you a new 60-250mm if they haven't been able to fix it after all this time.