it’s not the mirror that is faulty. that obviously works perfectly. it’s the object in the mirror with the roughness and the reflection on it that produces it. if you reflect diffuse materials or materials above 0.4 roughness, they are just fine. you gotta be aware of that. you can reflect glass and chrome maybe sparkly metal car paint if it’s within visual rough threshold. everything else should be a natural diffuse rough mix. ambient reflections. shiny doesn’t really work. unless it’s a “flat” reflection. car paint btw has 2 layers. the paint and the clear coat reflection. that is usually flat and you blend it with the paint color. that’s the way for your example. maybe you should change the shader.