strange reflective border

Hy render dude! I've got a quest for all the expert
Sometimes when i use default glossy, shiny or brushed materials (like metals, mirrors...) on some borders i obtain strange artifacts reflection (see image below). I tried to follow the also know and useful tutorial "sparkles, black and white dots, noise on materials?" without any improvement
Could anyone help me?
Thank's for supporting!

Sometimes when i use default glossy, shiny or brushed materials (like metals, mirrors...) on some borders i obtain strange artifacts reflection (see image below). I tried to follow the also know and useful tutorial "sparkles, black and white dots, noise on materials?" without any improvement
](./images/smilies/kt_wall.gif)
Could anyone help me?
Thank's for supporting!
