Did you make any changes to the "FTL Assist Me" mapped key? Or the FTL Modifiers in your Character Set?

If not, then here's what gets sent to make everyone assist.
Slot 1: Shift+Backspace
Slot 2: Right Shift+Backspace
Slot 3: Ctrl+Backspace
Slot 4: Alt+Backspace
If you changed the Key Combination used by "FTL Assist Me", you would replace the "Backspace" in each slot above with your new Key Combination. So if you changed it to F10 for example, it's Shift+F10, Ctrl+F10 etc.

If the ones that use Shift work 100%, and the ones that use Ctrl and Alt do not, then it sounds to me like you have Key Bindings in WoW (or Key Combinations in WoW Macro Actions from ISBoxer) using Ctrl+Backspace and Alt+Backspace (or e.g. Ctrl+F10 and Alt+F10)