Is it down to a badly written contract, lacking the finer details which only come to light once the system is "running"?
DS, you are probably correct with that. It is all the little extras that we as military personnel just do, because of years of experience, because it s what is expected of us and because when tasked with doing it by the Boss we get on and do it. The little things that would be impossible to capture in a contract but wich are the glue that holds the whole system together. Things like if the PowerPoint presentation provided by the provider (be that RAF or contractor) is wrong, you just get on and change it. But with contractor provided PowerPoint that is a contract change, requires negotiation and time, effort and (significant) amounts of money.
And that is where the logic of contractorization fails. The company need to make a profit (unlike the military). Your short term contracted service may be cheaper on paper, initially, but it will not remain so. Their costs will increase, there will be things we want to do that were never captured in the contract, we will need to make changes against the 10 or 15 year old plan, they will not be able to deliver the quality we require over time = more expensive, less effective, more frustrating than doing it all in house.