Hi Pavel,
it seems to be a bug. My suggestion downgrad to 6.3.1. That work.
TeeTanne
Convert destroys IPTC data in 6.3.3.2-Q16-windows-dll
Re: Convert destroys IPTC data in 6.3.3.2-Q16-windows-dll
We have a patch in ImageMagick 6.3.3-3 Beta to fix the problem you reported. A release version will be available within a week. Thanks for the problem report.