DA 16-85, AF Not Quite Locking In

I am curious if any other of you owners of this lens have had issues with your DA 16-85 lens developing a reluctance to reach final focus in auto-focus mode?  I really like my 16-85 a lot, but after a few months of light use it now consistently fails reach focus without 4 or 5 shutter half-presses to nudge it.  And in some cases it simply never quite locks on and I have to use the focus ring to allow the shutter to release.

I use the lens on a K5IIs.  I have the DA 50-135 and DA 300 SDM lenses which function correctly on the same body (both have had SDM motor replacements FYI).  I have also tried the misbehaving 16-85 on my son's K3 body and it exhibits the same focus lock problem.

To say I am dissappinted is an understatement.  Every SDM, or now DC motor, auto focus Pentax lens I have owned has developed AF issues.  Thank goodness I've kept my trusty screw-drive DA 16-45 and Tamron 28-75 F2.8 lenses. They snap into focus quickly and reliably without fail after years of use.

At least this time the problem occurred within the warranty period. My previous two SDM lens failures cost me a combined $550 to get fixed.  And the DA 50-135 had to be fixed twice.

As I wrote, I really like the DA 16-85.  It is for me, the perfect travel zoom... Adequate range, weather resistant, very good image quality.  I very much hope a warranty repair will solve the problem for as long as I continue to own it.