I used the button edit feature and added the following macro

#showtooltip
/cast [mod:ctrl,@player] [@cursor] Sigil of Flame

Assigning key bindings such as 1 or F to the button makes it work as expected with and without holding down the ctrl key. However, the button fails to work with some specific key bindings such as F5 or F6!!!

I do not have any other addon that uses these bindings and I have checked all the bindings in the "Key Bindings" interface to make sure they are not used.

The reason I am reporting this as a bug is that the same macro and keybindings (F5) work in other action bar addons.

Are you 100% sure you don't have anything bound to f5 or f6? Someone reported the same issue a couple months ago and it was that they were bound to some obscure thing in blizzard keybinding window

It's definitely a bug, I get a click noise trying to mount after playing a while using Shift+ MWheel Up. A reload doesn't always fix it but relogging does.

Someone reported the same issue a couple months ago and it was that they were bound to some obscure thing in blizzard keybinding window

You were right, though it was not a blizzard binding but a disabled addon that had ctrl-F5 key binding. I am not sure how a disabled addon can still affect the bindings, had to enable all addons to figure this out 💃