Canada problems were not fully resolved.
Jun.21 (GMM) Mercedes' reliability worries are not over.
In Canada, Lewis Hamilton failed to finish, while Nico Rosberg nursed his ailing W05 to just second place as the otherwise utterly dominant German squad struck cooling problems with its energy recovery systems.
In Friday and Saturday practice at the Red Bull Ring, the problems were back.
"No, unfortunately not," said team boss Toto Wolff, when asked by the Austrian broadcaster ORF on Saturday if the Canada problems were fully resolved.
"We still have aches and pains that we have not resolved but we need to for the race. It's much like the cooling issues in Montreal.
"The sword of Damocles is hanging over us," admitted Wolff. "It's not dramatic, but it's costing us performance. We need to resolve it."
On Saturday morning, it is believed Mercedes' troubles contributed to Valtteri Bottas setting the fastest time in the final practice session before qualifying, even though Wolff said the Mercedes-powered Williams is simply "fast" in Austria.