X31 screen with artifacts

[Paulpix]

Hi, suddenly the screen of my old X31 started displaying strange artifacts. I disassembled the motherboard and replaced all the tantalum capacitors, but the problem remains unresolved. A VGA external monitor works properly so I guess it's not a GPU issue. Is there any particular component placed between the GPU and the LCD connector that could be responsible for this?

https://ibb.co/8LdGwXfh

[Mr tom]

Looks a lot like flexing to me, i.e. some balls of the GPU BGA soldering lost contact,
usually due to torsion of the bottom case and/or vast differenes in expansion coefficients of involved materials.
Best use the notebook only on flat surfaces, to put on lap etc get a ~ 3mm Aluminum sheet of its size,
that also decreases avg temps by 2 to 4 °C here.

If this is indeed flexing and what i see is about the worst it gets,
there is a good chance that a well performed reflow can fix the issue, at least for a time.
Average life expectancy of mostly T4x reflows was 1.5 to 2 years here with regular use, positive statistical outliers up to 10 years.

Undervolting the CPU to limit heat will reduce the stress and prolong life in any case

[Paulpix]

Yes, you might be right. I've noticed that every now and then (although rarely) this issue disappears, and the screen works properly for a while. This makes it likely that it's not permanent physical damage to a component, but rather a faulty connection somewhere. I'll try to follow your advice. Thanks.