How old is the save you are currently using that is bugged? In my larger settlements, it can take 5-10 minutes between assigning a peon and getting the assigned message, with the latest unofficial patch (but my computer is a bit older, so CPU horsepower has a bit to do with that). On my laptop, I have to keep my FO4 slim, so I only run a small handful of mods (scrap everything, place everywhere, masterplan/vanilla extensions, no settler/ai mods) and I've had that bug too, so I do not think it is DCMS.
and also keep in mind the papyrus-beast the runs amok in your game behind the scenes. Seems like sometimes that sumbitch just chews on the wrong thing and everything goes to hell