I really think space is your problem. There just isn't enough room for them to get away, and with the current set up, there are corners where they can be cornered/trapped. Your true 'coop' (that's the house part) dimensions look more like 3.5 x 5 x a little less than 2. To expect 8 birds to roost in there comfortable is dreaming. My suggestion would be to enclose the entire coop (or build something bigger) as it is now so that the entire 7 x 5 x 3.5 is enclosed house/coop. And to increase your run size (the part that isn't house) by at least double. Those premade coops always way over estimate the amount of birds they can really hold, and depending on the personalities of your individual birds, the actual space needed can vary greatly. Usually the minimum recommendations are coop space 4 square feet per bird, run space 10 square feet per bird, roost space 10-12" per bird. Those are minimums and recommendations, but in practice you may need more or less, depending on your birds, whether they spend more time in the coop (will they need to be inside more during winter?- more space needed), whether they free range, etc. When you have behavior or bullying problems, space is very often the issue.