K1 & FA 50mm f1.4 lens fine focus calibration issue

So I've adjusted the FF on the K1 for my lenses but the 50mm gives me issues.
I've a sheet of paper angled at 45 degrees away from me with horizontal lines on it. 2 sec self timer set, set to f1.4, focus on the middle line & take a shot. Zoom in on shot image & it shows front focus. Don't alter anything but place hand in front of the lens to force focus to change, remove hand, focus on the middle line again & take a shot. Zoom in & now the line's in focus. Repeat & this time there's front focus again. Repeat & middle line's in focus.
So the camera isn't finding the same focus point each time meaning any fine focus adjustment isn't final.
I've made adjustments 3 times previously & still been left wondering why some shots aren't sharp. If the combo finds a different focus plane each time any adjustment isn't likely to work.
Anyone any idea what's going on? Why's this particular camera/lens combination giving differing focus results.
I'm baffled as my other lenses once adjusted have remained ok.

That happens with PDAF, although a 50% miss ratio is very poor. 10% is quite normal


I would give the AF sensor a blow with a rocket blower in case you have dust on it, but its a long shot.

Do you notice how the accuracy compares when you get the lens to focus from infinity versus from closest focus distance ?

Must admit I hadn't tried it at the extremes, I'll give it a go.
A quick blow around with the rocket can't hurt either.
Thanks for the input

Mirror up and the AF sensor is in the bottom of the mirror box

Do 10 tests from each extreme to get an accurate assessment.

I just recently bought a K1, to say it’s a disappointment is an understatementi.
It doesn’t focus properly.

The K1 is a superb camera, there's obviously something wrong somewhere, care to elaborate on " it doesn't focus properly " what lens are your using, settings etc ?

The k1 focusses perfectly, you are doing something wrong.

Wow, that's a bold statement, although unlikely it may just be a duff camera.

Indeed it may be. But without any information from the poster about what his settings are, and some images to diagnose, I have no idea.

The K-1 has been in production for 5 years now. If it had a general focussing issue I think it would be apparent by now.

The most common mistake is someone moves from an older camera to a 36MP sensor unit like the K1. They then look at the images at 100% and see that focus is off without realising it was just as inaccurate on their older camera.

There is a reason all manufacturers have AF adjustment menu items.

Exactly, so before declaring him incompetent perhaps it would be better to find out those settings because if you look back at his previous post he has been a long time user who is probably fairly well clued up on how to use a Pentax body

I am so used to folk moaning on forums of all types these days that I give these kind of posts short shrift.

If he wants help i have lots of experience fine tuning lenses with the K-1, and have offered that help on many occasions.

If he wants to just gripe I have no time.