There isn't a lack of information flow from the field to headquarters. In fact, there is probably sometimes too much information, and it's a matter of culling it. There are daily reports, cables, and an entire centre set up to receive information and flash reports and other things.
The more interesting part is how you shift gears and make changes over time. There is a process of strategic reviews that goes on which is increasingly independently led. It assesses what the direction of the mission is, how well it is meeting its objectives and whether changes need to happen. That can be driven by a crisis, as happened in 2013 with the civil war in South Sudan. It can be driven on a regular basis; it can be mandated by the Security Council, and it can also be mandated by the UN Secretary-General. That's the traditional way of shifting gears.
What you also see in some missions now is a lot of innovation on the ground that is being fed back. The creation of intelligence capacities in places like Mali and Congo was largely an innovation which arose out of a need on the ground. That filters back into new policies that are now driving other missions as well, so there is also quite a lot that happens on the ground that feeds back in and creates a loop.
Then there is obviously annual mandating, where a mission can shift gears based on the UN Secretary-General's report. That is fed from the ground as well.