Set Actor Location of a hierarchical instanced mesh causes performance issues

Hello dear community, I have a problem.
In my game, I want to move a hierarchical instanced mesh. This mesh consists of max 1000 instances, all of the same type. The instances are simple boxes (12 tris) and a very simple uv texture. The move itself is a very basic command: Press a key and the mesh moves 1000 units in the x direction. Still the game freezes for about a half second. Performance analysis told me, I am CPU bound, further analysis (profiler) shows that the CPU is mostly doing nothing (waiting, stall, sleeping). Unfortunately, I do not see where the problem hides as well, the profiler shows no activity that has such a high calculation time or was called so often to slow the game thread in such a way. To speak in numbers, while I move the mesh the game thread needs ~300 ms to render, the few calculations that happened took only a couple of milliseconds. There were calculations that were called over a hundred times, but they took only a fraction of a milliseconds to fulfill.

Has anyone an idea of that is going on and maybe how to fix it?