Gfilui

I'm running Kubuntu 18.04 on a 2014 MacBook Pro 13". I followed this answer and got 99% of the way there. However, I'm having a problem cycling through my open windows. In System Settings > Global Shortcuts, I set "Walk Through Windows Alternative" to Ctrl+Tab so that I can switch windows with the physical Command and Tab keys like on macOS. This seems to work fine when I press the physical Control and Tab keys. However, the problem arises when I press the physical Command and Tab keys. Instead of being able to cycle through my windows and choose whichever one to switch to, I am switched immediately to the most recent window. It is the same action as pressing and releasing the physical Control and Tab keys. I am unable to hold down the physical Command key and cycle through my list of open windows.

Here's the output of xev -event keyboard after pressing the physical Control key then the physical Command key:

KeyPress event, serial 28, synthetic NO, window 0x4c00001,
 root 0x169, subw 0x0, time 1734412, (113,120), root:(113,181),
 state 0x0, keycode 37 (keysym 0xffe3, Control_L), same_screen YES,
 XLookupString gives 0 bytes: 
 XmbLookupString gives 0 bytes: 
 XFilterEvent returns: False

KeyRelease event, serial 28, synthetic NO, window 0x4c00001,
 root 0x169, subw 0x0, time 1737452, (113,120), root:(113,181),
 state 0x4, keycode 37 (keysym 0xffe3, Control_L), same_screen YES,
 XLookupString gives 0 bytes: 
 XFilterEvent returns: False

KeyPress event, serial 28, synthetic NO, window 0x4c00001,
 root 0x169, subw 0x0, time 1738724, (113,120), root:(113,181),
 state 0x0, keycode 133 (keysym 0xffe3, Control_L), same_screen YES,
 XKeysymToKeycode returns keycode: 37
 XLookupString gives 0 bytes: 
 XmbLookupString gives 0 bytes: 
 XFilterEvent returns: False

KeyRelease event, serial 28, synthetic NO, window 0x4c00001,
 root 0x169, subw 0x0, time 1742108, (113,120), root:(113,181),
 state 0x4, keycode 133 (keysym 0xffe3, Control_L), same_screen YES,
 XKeysymToKeycode returns keycode: 37
 XLookupString gives 0 bytes: 
 XFilterEvent returns: False

Here's the output of xmodmap:

xmodmap: up to 4 keys per modifier, (keycodes in parentheses):

shift Shift_L (0x32), Shift_R (0x3e)
lock 
control Control_L (0x25), Control_R (0x69), Control_L (0x85), 
Control_R (0x86)
mod1 Alt_L (0x40), Alt_R (0x6c), Meta_L (0xcd)
mod2 Num_Lock (0x4d)
mod3 
mod4 Super_L (0xce), Hyper_L (0xcf)
mod5 ISO_Level3_Shift (0x5c), Mode_switch (0xcb)