https://www.as-web.jp/f1/641490/2
Translated from a German site:
In Q2 of qualifying, Verstappen came in after his first fast lap. The Honda engine struggled and he wanted the problem solved before going for his second fast lap. Ultimately, it was a faulty spark plug, part of the engine's ignition system.
"It was impossible to predict when that problem would occur," says Tanabe when asked about the RB16's sputtering engine. 'Our durability tests show how long each part can last. We use the parts with a small margin on them as well. '
That is why the defect came as a surprise to Tanabe: "In principle, the spark plug should have lasted." Again, Honda is struggling with motor problems at a Red Bull that occur unpredictably: "This was also an incidental problem."