It looks like that Metz has again this problem. I had the same behaviour happen with K-3 and Metz 52... I reported that to Metz Deutschland and on my behalf they modified firmware to eliminate this. Here are some of the emails with them... just the relevant ones...
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Thank you very much for your e-mail and for details.
In the meantime we forwarded your e-mail to our development department.
Now, we also found that flash unit fires randomly by itself, however this happens very very seldom here.
To solve this problem we guess flash unit’s firmware needs to be improved. However, this may take some time. Unfortunately, a fast solution of this problem is not possible.
We will you inform by e-mail as soon as a new firmware version for your flash unit is available.
With kind regards
Wolfgang Becker
Technical Support
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As of now a new firmware version (1.3) for the flash unit mecablitz 52 AF-1 digital for Pentax is available by which the mentioned problem is solved. This new firmware can be downloaded from our homepage by following link:
http://www.metz.de/en/flash-units/firmware-download-flash-units/mecablitz-52...al/pentax.html
Best regards
i.A. Roland Laemmermann
Technical Support
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It took them around 3 months to solve this. I had did also some tests with various lenses and submitted the results to them which helped them isolate the problem. I do not have K-1 or the Metz 58 to be more helpful with this.
The volks at Metz are good and if reported properly, backed up with solid and exact behaviour reference point they will take it right away into development centre for the resolution