E6430 Artifacts while external display

Hello people,

i have problem with my old E6430, which i recently got. 

The problem is in artifacts, that appears when i connect some external display. The artifacts shows on display of the laptop (not on the external one) and appears only occasionaly in irregularly intervals. More, when I work on the laptop.

Doesn't matter which port I use. (D-Sub, DVI, HDMI ) I tried every possibilities including docking station, which I am using as prime.

I'm using windows 10 64bit and tried win7 as well, with all up to date drivers and bios. Nothing helped. I tried dell online diagnostic and it showed me, that everything is ok..

I already tried all my ideas. 

Please, do anyone know any another posibility. What can cause these problems?

Thanks a lot for whatever...