Since one of the more recent updates, blueprints can be placed on top of things that are marked for deconstructions (in fact you can even force-place the blueprint and automatically mark trees for deconstruction). However, for some reason bots will prioritize the task of building over the task of deconstructing.
That means that whenever you have a limited amount of construction bots and you construct something big enough, all the bots will swarm out with items to place down. However if there's still something in the way they just end up hovering and waiting forever while no bots are left to actually deconstruct the things that are in the way. This happens both with static and personal roboports.
The only way to resolve this situation is to deconstruct everything (often after parts of the new blueprint have already been built) and wait until it's completely done, than place the blueprint again. Quite annoying.
Solution is simple: Prioritize deconstruction jobs over construction jobs.
