I have noticed that, if lyx is started from a terminal where LANG="it" has been set, margins cannot be changed by non-integer values.
As /etc/environment with LANG="en" is sourced, lyx allows for non integer changes (in cm units). Notice that, as non integer margins have been set, editing the same doc by lyx, in the LANG='it' environment do not change margins in the final pdf form, but only the integer part is displayed in the document settings panel, while trying to change the decimal part of margins is ineffective. Any idea? thank you -- Pol