When i run 'make menuconfig' i get broken lxdialog UI. Unfortunately i don't know how to attach an image here. It looks like blue stripes and characters meshing in some submenus.

The same on 'make kernel_menuconfig'.

If i comment out both LC_ALL:=C and LANG:=C lines in the root Makefile then UI is displayed correctly.

If i run 'make LC_ALL=en_US.utf8 menuconfig' it works for menuconfig but not for kernel_menuconfig.

Is this an issue of OpenWRT configuration scripts or something wrong with the ncurses library? (I have ncurses 6.0+20170902-3 under Arch Linux)
Menuconfig of vanilla kernel and all other ncurses applications are displayed well.