S2715H input source

Monitor: S2715H

Issue: input source keeps changing - the monitor goes dark for a second and then comes back on with the input source displayed on the screen ( just like when you go into the options meniu of the monitor and change it;s input source) and keeps on cycling through this until you unplug it. i can;t power it off or access its menu after this starts happening. it does so for a minute or so and then turns off.

Note: i've bought this monitor 2-3 months ago and it has shown this behaviour a couple of time. also if i unplug the vga or hmdi cable it keep going on and off. the cables aren't plug in at the same time. i just tried it with both of them. also i tried changing the monitors option from auto-select input source to a fixed one hdmi or vga with no success this still keeps on happening. this behaviour doesn't seem to be dependent on some sort of event .. just happens i could be playing, browsing the web or just have it sitting there with only the background processes working...

S/N: CN-0720XR-74445-69u-ahyl

Rev A03

it is connected to an ideapad 300 lenovo laptop. resolution 1920x1080

bought from a distributor 

can someone tell me if there's something i need to do, or if this is faulty device?

thank you!