Sebastian Vettel is set to drive his third new chassis of the 2014 season, after suffering more mysterious handling problems in Belgium last weekend.
"I can't explain why my car could not compete with Daniel's at this race," Vettel, referring to Spa, is quoted by Sport Bild.
"But there must be something. Both cars are identical and so they should have the same performance."
Team official Dr Helmut Marko agrees.
"It is not normal for Sebastian to lose so much time to Daniel," he is quoted by Auto Bild Motorsport.
"I can understand how frustrated he is, especially as his teammate won. We will build a new chassis for him as quickly as possible."
Meanwhile, Red Bull has confirmed reports Vettel's long-time race engineer Guillaume 'Rocky' Rocquelin has been promoted to chief engineer for 2015, as Adrian Newey takes a step back.
"Seb has had a long chat with him (Lambiase) and they hit it off immediately," Marko said.