The need to reposition the screen does indicate a hardware issue.
As to not sure, I agree. The only way to be sure is to try a new cable. No technician I know will commit to a solid diagnosis but it does sound like the right diagnosis. I'd change it since it's the cheapest thing it could be.
I have a sony vaio SVE171390X 17.3". After it starts the screen gets white(not everytime but sometimes), i have to reposition the screen in order that the image to get clear. After some time the screen gets white again, and I have to repostion the screen again. Some technician that saw this problem said that was the fault of the LCD cable of the screen, but they were not sure.
If someone would give me any advice I would be very greateful.

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