Intermittent horizontal lines on my Kindle Paperwhite 2 screen – hardware issue?

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Hi everyone,
I recently bought a used Kindle Paperwhite 2 (6th generation), and I'm having an issue with the display.
The screen sometimes shows thin horizontal white/gray lines across the entire display. Interestingly, the lines are intermittent: sometimes they disappear completely and the screen looks perfectly normal.
The problem is not limited to books. The lines can also appear on the Home screen, Settings, and even during the Kindle boot/logo screen.
I have already tried a forced restart by holding the power button for about 40 seconds, but the problem still occurs.
I also noticed that the lines can sometimes remain visible when the Kindle is asleep/off.
Does this look like a failing E-Ink display, or could it be a loose/damaged display connection or another hardware issue?
Is there anything I can try before considering a screen replacement?
I've attached some photos showing the problem. Any advice would be greatly appreciated.