That is my number 1 concern before I got my lens. Hopefully, my lens doesn't have that problem. It seems like a common issue for this lens which I blame Pentax. SO… After not using it in a while, try to help it wake up by manually turn the focus ring a bit then try autofocus. After it wake up, it should continue to work well throughout your shooting day.
I would return the lens if:
1. It take too loooong to wake up. Let’s say more than 3-5 second even with the help of manual focus.
2. the problem repeatedly comes back during a shooting day after it wake up.
Keep in mind that the lens is a known slow auto focus lens. A millisecond of time lack can be expected when you hit autofocus button. And make sure your auto/manual switch on the lens is not at manual. I accidently switch it to manual all the time.
Last edited by tokyoscape; 02-12-2019 at 09:16 PM.