how can I solve this problem?
I’m afraid that you need to give us a bit more information. Are you using Unreal Engine 5.1? Does your scene contain a cube reflection capture actor?
In the case of your mirror, it looks like you should use planar reflections if you aren’t already. See https://docs.unrealengine.com/5.1/en-US/planar-reflections-in-unreal-engine/ for more information on how to achieve this.