"token timeout", so I have to write everything again
. Well, I'll be quicker this time.
It seems K-S2 has a firmware bug, that sets the ISO in P + auto ISO mode with external flash to maximum value and so overexposing the picture, by 5-7 stops. I can set the ISO by hand and I admire all who want to set the exposure manually, but it is not me, and probably never will. The P-TTL was created to make the settings automatic, and here, unlike on my Nikon, it simply does not work. I can see pre-flashes, but the metering system seems to be fooled by otherwise complete darkness, sets the ISO to max and overexposes. Annoying.
Of course it might be I missed something, there is a setting that will make it work, but so far I have not found it.