The bias was unexpectedly sent fully to the front, causing the American driver to lock up and slide into a run-off area at Turn 4.
After initially believing that he would have to retire, Sargeant was able to drive back to the pits and resumed after swapping to a new steering wheel. The change appeared to address the problem, but he eventually finished a distant 20th.
"With Logan, we have an uncommanded brake bias movement all the way to the front, which is why he went off," Vowles told Autosport. "The brake bias moved nowhere near where he requested it to be."
Sargeant admitted he couldn't comprehend what was happening when he first had the issue.
"It was just doing things on its own without my asking," he said. "I don't completely understand it from my side.
"We've had some electronic issues the last couple of days, qualifying and then today. So we just need to understand the core issue. We thought we fixed it, but obviously it came back.
"It didn't happen again, once we changed the steering wheel, so maybe it's something there. But we just need to understand the core cause for it, and try to not let it happen again."
Both Sargeant and his team-mate Alex Albon also had to deal with unexpected power unit temperature problems during the race, which Vowles insisted disguised "a much faster car".
Source: Autosport