The opening hour-long run at Melbourne's Albert Park needed to be red-flagged for seven minutes due to a loss of GPS data.
The outage meant the teams were unable to relay messages to their drivers with regard to track positioning in relation to other cars behind, in particular, those on quick laps in comparison to those on warm-up or slow-down laps.
It resulted in traffic chaos and a few near-misses for a short period before a decision was taken to halt the session to allow the GPS to come back online.
“Seemed like everyone was blindfolded once that GPS system went out,” said Haas driver Magnussen. “Yeah, old school, I guess.
“It's also because we know we're relying on our engineers to tell us where the traffic is. I don't think everyone knew that the GPS was out.
“So when you don't hear anything, you expect there's nothing coming, whereas if we didn't have a GPS system, you'd be way more careful and just looking in your mirrors the whole time. And nobody was.”
Practice highlighted driver differences – Hulkenberg
Team-mate Nico Hulkenberg was one of those forced to avoid a collision as the German had to take action to avoid hitting Lando Norris in his McLaren, resulting in him locking up and taking to the grass at the penultimate corner.
After declaring himself “just very good at watching my mirrors”, Hulkenberg added: “Some drivers rely more on their engineers and their calls than others.
“Obviously, I think in a situation like today that's when it comes out, or you see the difference, I guess.
“Also, (as it is) a street circuit, there are quite a few spots where it's blind or you see a come a car come around quite late, which doesn't help and makes it a bit sketchy in a place like here or Jeddah or street circuits.”
The German driver agreed that race control was “right” to stop the session in order “to fix the problem”.