Description of problem:
For some reason pressing any alt key (including <MENU>) together with <LFSH> toggles "Switch windows of an application". This can be turned off by commenting out

 key <LCTL> { [    Tab,      Tab,       Tab,         Tab  ] };

in my xkb layout file. However, I would like to keep remapping left control <LCTL> to Tab. How can I do this without causing the above behavior?

Version-Release number of selected component (if applicable):
I am using Fedora 20 with kernel 3.14.7-200.fc20.i686.

How reproducible:
Always.

Steps to Reproduce:
1. Create entry in /usr/share/X11/xkb/symbols/us

partial alphanumeric_keys
xkb_symbols "workman-d" {

    name[Group1]= "English (Workman special)";

    include "us(workman)"

    key <TLDE> { [ grave, asciitilde,        degree,           degree ] };
    key <AE03> { [     3, numbersign,       section,          section ] };

    key <TAB> { [    BackSpace,       BackSpace,       BackSpace,        BackSpace ] };
    key <AD01> { [     q,          Q,            at,               at ] };
    key <AD08> { [     u,          U,    udiaeresis,       Udiaeresis ] };

    key <CAPS> { [    Control_L,       Control_L,       Control_L,        Control_L ] };
    key <AC01> { [     a,          A,    adiaeresis,       Adiaeresis ] };
    key <AC02> { [     s,          S,        ssharp,           ssharp ] };
    key <AC08> { [     e,          E,      EuroSign,         EuroSign ] };
    key <AC09> { [     o,          O,    odiaeresis,       Odiaeresis ] };

    key <AB04> { [     c,          C,          cent,        copyright ] };

    key <LCTL> { [    Tab,   Tab,       Tab,         Tab  ] };
    key <LFSH> { [ Shift_L,     Shift_L,      Shift_L,        Shift_L ] };
    key <MENU> { [ Alt_R,      Alt_R,         Alt_R,            Alt_R ] };

};

2. Restart X.
3. Hold down <MENU>, then press <LFSH>

Actual results:
"Switch windows of an application"

Expected results:
Nothing.

Additional info:
The xev output is

    keycode 64 (keysym 0xffe9, Alt_L) from pressing left alt
    keycode 50 (keysym 0xffe1, Shift_L) from pressing left shift
    FocusOut event, serial 36, synthetic NO, window 0x2a00001, mode NotifyGrab, detail NotifyAncestor from pressing left alt + left shift