The whole structure is wobbly (but not just-about-to-fall-down wobbly) because the only thing holding it up is 2x4s and the metal CS14 wrapped around it. Wood flexes, of course, so standing in the loft can be nerve wracking.
The fix is to add plywood sheathing.
Once the sheathing is added, I cover it with Tyvek. This is a permeable plastic that allows water vapor to escape from the wood, but doesn’t let water in.