Originally posted by hectorse Using phase detection focusing, it just doesn't get tack sharp and front focuses very heavily, so much that even the microfocus adjustment menu is not able to compensate at -10. This is something I've encountered in my K-5 with the DA* 50-135, and was able to fix it by going into debug mode and adjusting to need.
I'm kind of surprised the DA 50-135 was off so much. I've had a couple FA lenses that just wouldn't play with my K3 and ended up selling them.
You can try the repair route if you have a good place locally, but given the value of the lens, I don't know if it's worth the effort. You may just end doing what I did, which was selling it at a discount and picking up another copy that fits within your camera's tolerances.
I have one lens that was probably a -11-ish on my K3, but I held onto it, because it was a pricier piece of FF glass. On my K1, it's a -2. Go figure. Chances are your lens will work great on someone else's K1. Maybe time for it to find a new home.