So I've found 2 things so far that the Metz 52 AF-1 doesn't do on the K-1.
1.) The lcd on the back of the flash doesn't light when the shutter is half pressed. (It does with my K3II.)
2.) The red AF illuminator focus aid beam doesn't light up. (It does on my K3II)
I make no claims as to having everything set correctly. I just learned a few minutes ago how to turn on the movie mode!
The flash exposures seem to be very nice.
And I did upgrade the Firmware on the flash to v. 1.3 Camera FW was 1.30.
The Metz 52 AF-1 is my go to wedding flash these days, been doing great service this season.