Thank You for your response. Really appreciate. Will try to get in touch with store and see if they help.
Is there any software to test vram? I would like to check before I tell those peasants working at a service center.
yes try and launch a game as soon as it starts loading in textures what will be 6gb only if one or more chips came lose it would not have those 6gb of vram to loud in the textures so it will crash. benchmarks, on the other hand, will mostly not load in as many textures as a game so the card will still be fine.