Sometime macros run slower using shortcuts

[Eadden]

Hello,

So here's my problem, I have a range of cells I want to shift (with some conditions) so I have macros to do it (shiftLeft, shiftRight). First the user needs to select the range, then run the macro through a shortcut (ctrl+alt+Left|Right).
But I noticed it is much slower with shortcuts than pressing F5 in the VBA IDE. Around 3.3 seconds instead of 0.5 seconds.
Obviously I turned off screen updating, events and put calculation on manual.

Moreover, if I first try with a shortcut (runs slow) then try pressing F5 in the IDE (runs fast) and finally trying again with a shortcut, it runs fast as if I just pressed F5.

So I was wondering where does this behavior come from ?
Did I do something wrong ?
How can I fix it ?

Thank you

[#2]

@Eadden 

What happens if you run the macro using the shortcut (slow), then run it again using the shortcut? Is it faster the second time?

[#3]

Running it again with the shortcut isn't faster, it's still slow

[#4]

@Eadden 

Sorry, no idea...