And this is the xev output for same keys when they stop to work:

KeyPress event, serial 37, synthetic NO, window 0x5200001,
    root 0xbf, subw 0x0, time 154792805, (615,169), root:(2120,1266),
    state 0x10, keycode 36 (keysym 0xff0d, Return), same_screen YES,
"   XLookupString gives 1 bytes: (0d) "
"   XmbLookupString gives 1 bytes: (0d) "
    XFilterEvent returns: False

KeyRelease event, serial 37, synthetic NO, window 0x5200001,
    root 0xbf, subw 0x0, time 154792883, (615,169), root:(2120,1266),
    state 0x10, keycode 36 (keysym 0xff0d, Return), same_screen YES,
"   XLookupString gives 1 bytes: (0d) "
    XFilterEvent returns: False

KeyPress event, serial 37, synthetic NO, window 0x5200001,
    root 0xbf, subw 0x0, time 154801177, (615,169), root:(2120,1266),
    state 0x10, keycode 103 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes:
    XmbLookupString gives 0 bytes:
    XFilterEvent returns: False

KeyRelease event, serial 37, synthetic NO, window 0x5200001,
    root 0xbf, subw 0x0, time 154801274, (615,169), root:(2120,1266),
    state 0x10, keycode 103 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False

KeyPress event, serial 37, synthetic NO, window 0x5200001,
    root 0xbf, subw 0x0, time 154818131, (615,169), root:(2120,1266),
    state 0x10, keycode 120 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes:
    XmbLookupString gives 0 bytes:
    XFilterEvent returns: False

KeyRelease event, serial 37, synthetic NO, window 0x5200001,
    root 0xbf, subw 0x0, time 154818231, (615,169), root:(2120,1266),
    state 0x10, keycode 120 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False

KeyPress event, serial 37, synthetic NO, window 0x5200001,
    root 0xbf, subw 0x0, time 154825928, (615,169), root:(2120,1266),
    state 0x10, keycode 149 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes:
    XmbLookupString gives 0 bytes:
    XFilterEvent returns: False

KeyRelease event, serial 37, synthetic NO, window 0x5200001,
    root 0xbf, subw 0x0, time 154826006, (615,169), root:(2120,1266),
    state 0x10, keycode 149 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False

KeyPress event, serial 37, synthetic NO, window 0x5200001,
    root 0xbf, subw 0x0, time 154828324, (615,169), root:(2120,1266),
    state 0x10, keycode 93 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes:
    XmbLookupString gives 0 bytes:
    XFilterEvent returns: False

KeyRelease event, serial 37, synthetic NO, window 0x5200001,
    root 0xbf, subw 0x0, time 154828420, (615,169), root:(2120,1266),
    state 0x10, keycode 93 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False

KeyPress event, serial 37, synthetic NO, window 0x5200001,
    root 0xbf, subw 0x0, time 154829805, (615,169), root:(2120,1266),
    state 0x10, keycode 97 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes:
    XmbLookupString gives 0 bytes:
    XFilterEvent returns: False

KeyRelease event, serial 37, synthetic NO, window 0x5200001,
    root 0xbf, subw 0x0, time 154829916, (615,169), root:(2120,1266),
    state 0x10, keycode 97 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes:
    XFilterEvent returns: False