Buxus
B. sempervirens_boxwood_box_krušpánek_zimostráz_??? Whatever name you like, it is all about the same hardy plant. Hardy? For sure the bush is quite resistant to the attacks of many pests but as we know a keen non well seasoned greenfinger or a delicate moth could do a lot of damage to it. Just have a look how this tree has looked like in spring 2018: And now in winter ( 30.12.2019 ) It looks a bit less regimented perhaps. But if you look closer you will see a lot of dead branchlets all around the crown. See the pic below... At the first thought about the reason I was quick to blame the vigorous blossoming in the previous year. And based on that I have tried to strip as many new buds as possible. Quite a job. You need a good amount of time to deal with that. The good point of it - it gave me a lot of time to think. And maybe having a bit deeper and more honest look on the possible root causes....