Is this a bug? Customization lost when changing language interface

LO under Win8.1 64 bit. OS language is Japanese, LO default language too. I have a set of customizations, in particular function keys assigned to some customized commands. If I switch the interface language to English UK, my customization is lost, if I switch back to Japanese the customization is back. Is this the way it is meant to work or it a bug?

Please, what customization is lost?

For example, I customized F11 as “save document”. When I switch to English interface, F11 is reverted to “Styles and Formatting”.