Not insulation breakdown (voltages too low) but poor impedance matching and "return loss" performance on the faulty pair, which would show up more at 8Mb than at 2Mb. Same end result really. Glad you managed to fix it.
OnePlus 5T review: Hands-on
Illustrator Andrés Lozano on his improv line work, brazen use of colours & hand sketching
iPhone X review
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