Well it is the poor management, rather that not enough.
You are right about not enough staff on certain flights, hence that boils down to management policies.
I know that another established handling company at STN had similar issues with manning, promised airline a certain amount staff on each plane, but never provided that amount of staff, no-where near, simply because they could not achieve what was promised.
So it is not just S/Air, that has these issues, Swissport flooded Ryanair to get flights sorted, now that FR is cutting 20% of its services, look what has happened, chopped jobs.... The balance of sufficent staff against over-staffing is a very fine line, as i said before, it all comes down to money.
As yet I have been able to unlock the gate outside BAA's plush complex to get to the money tree that they seem to have ...