Mercedes boss Toto Wolff has shared more details on the issues George Russell and Lewis Hamilton encountered during the Spanish Grand Prix.
Russell and Hamilton were both told to back off in the closing stages of the 66-lap encounter - amid baking hot Barcelona temperatures - due to a "DNF risk".
While Russell held on to third after a spirited battle with the Red Bull drivers, Hamilton lost fourth to Ferrari's Carlos Sainz, having fought his way back from a first-lap incident.
After the race, Wolff admitted that the separate reliability problems were worrying for Mercedes amid the team's step forward in performance.
"Yeah, there are some [reliability] concerns," he told media, including RacingNews365.com.
"We had a water leak on Lewis' car and general overheating on George's, and it's concerning, but we obviously need to look at the hardware."
Viewed by others:
Wolff: Mercedes have halved the gap to the front
Despite these reliability concerns, Wolff ended the event feeling encouraged by the significant progress his team has made.
Mercedes brought a host of upgrades to Spain, which appeared to greatly reduce porpoising on the W13 and enable the team to unlock more of the car's potential.
"I think we are literally learning by doing," Wolff commented.
"These regulations have caught us off guard in a way, and step by step we are understanding what we need to do in order to bring the performance back into the car.
"We've seen another big step this weekend, probably we've halved the disadvantage to the front-runners, but still there is lots to go in order to be right up there in the fight."
Mercedes remain third in the Constructors' standings, 49 points behind Ferrari, and 75 adrift of Red Bull.
Video: How much does it cost to become an F1 driver?
RacingNews365.com breaks down how much it costs drivers to make their way up the ranks in the world of motorsport and become an F1 driver.