Normhead, I found the post by Al for you. I won't comment much further, you can read his evaluation. I will say that I know Al as a qualified and experienced shooter of long standing with Pentax gear.
Like many of us, he saw the K5 as a perfect camera for portraits, weddings, etc, but after three K5's he gave up for the time being. From Falc's report and various reports from Pentax technicians ( not verified ) it would appear that this affects all K5's, but to what degree is debatable.
I read somewhere here yesterday of a K7 user that reports he has the same FF problem, which is intriguing, since this is not a reported problem with the K7, in fact quite the opposite. I am wondering if this could mean that his K7 has a "quirk" that is in the K5's in large numbers but not in K7's...which might mean a more simple repair? If so it seems we would already have a repair, but maybe it is not that simple? Maybe the K7owner has a hardware problem that was rare in the K7 but common in the K5? We could compare the sensor problem and see how it could be possible that a faulty hardware part could indeed slip by in a lot of K5's....maybe all of them? Just speculation on my part, but no matter what the outcome, I hope we do learn the source of this problem and are not left in the dark.
BTW- Al says the "animal" is a wolf whose snout broke off? Looks like a cat to me, but whatever, it should not affect his credibility as a fine shooter! LOL!
Best Regards
NOTE: Just discovered I was so busy running my big mouth I left out the link. Sorry!
https://www.pentaxforums.com/forums/pentax-k-5-forum/128562-relevant-news-re-...-light-28.html