Toto Wolff says a cracked fibre optic cable was to blame for Mercedes' communication issues during Sunday's Hungarian Grand Prix.
Both Lewis Hamilton and Valtteri Bottas struggled to communicate with the team during the 70-lap race due to an IT issue.
Wolff explained: "It was a local hardware issue. We found a crack in a fibre optic cable, that made us fly blind.
"Our whole comms and data systems broke down. We didn't have any communications on the 'Fantasy Island' – that is the middle thing we have – and on the pit wall.
"So no radio comms, no data, no TV feed. We somehow managed to get it back occasionally – and that obviously penalised us strongly.
"So there were conversations at times that Lewis heard and then there were conversations he didn't hear. A difficult one."
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The communication issue meant Hamilton was forced to pit earlier than he wanted with the Brit unable to tell Mercedes that his tyres were still in good shape and that he could stay out longer.
It also meant his request for Bottas to move over and let him through didn't reach the team soon enough, making it less effective.
"We could have had it a couple of laps earlier because he [Hamilton] told us he could have gone much quicker," Wolff said.
"He even said his tyres were in good shape the first set, and we could have tried to leave him out.
"That could have had a potentially massive outcome on the race as we were so close to the Ferraris in the end. But if and whens don't win you races."
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