Comment 24 for bug 255372

Same issue here.

KeyRelease event, serial 34, synthetic NO, window 0x3600001,
    root 0x13b, subw 0x0, time 169384988, (51,-18), root:(802,445),
    state 0x0, keycode 97 (keysym 0xff24, Romaji), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False

$ setxkbmap -print
xkb_keymap {
 xkb_keycodes { include "evdev(abnt2)+aliases(qwerty)" };
 xkb_types { include "complete" };
 xkb_compat { include "complete" };
 xkb_symbols { include "pc+br+inet(evdev)+level3(ralt_switch)" };
 xkb_geometry { include "pc(abnt2)" };

Section "InputDevice"
 Identifier "Generic Keyboard"
 Driver "kbd"
 Option "XkbRules" "xorg"
 Option "XkbModel" "pc105"
 Option "XkbLayout" "br,ru(phonetic)"
 Option "XkbOptions" "lv3:ralt_switch"
EndSection

Aside notes: I've been using ru_phonetic as 2nd layout and my kb has 111 keys (without multimedia).

Now going to test Rodolfo Lima's hack.