A1990 Display horizontal stripes

If it’s appearing as you open the lid, the yes, I would definitely think this is one of the cables between the TCON board and the display. Likely it is more related to actual image data, not backlight, backlight would typically just dim slowly as you open the lid further or cut out all together.

Unfortunately, if it is the cable (which i think is VERY likely given what you described), this is usually not an easy fix outside of replacing the entire display assembly because the cables in question are directly soldered onto the TCON board on one end, and the other end goes up behind the display panel, which is not something that is intended to come out of the housing and is fairly likely to break if removal is attempted.

These cables go right through the hinge area of the machine and it is not unusual for their connections to fail due to repeated stress from opening and closing lid. If the fault is in the soldered on end, it’s possible for them to be soldered back down, but it would need to be done by someone fairly skilled since the connections are small and the cable would be easy to damage with heat in the process.