Elon Musk, chairman and chief executive officer of Tesla Motors, exits the Model X sport utility vehicle during an event in Fremont, California, Sept. 29, 2015.

Consumer Reports has a serious problem with those falcon-wing doors.

The group, which once said a Tesla car was so good it broke their ratings system, has ranked Tesla 25th out of 29 auto brands in its 2016 Annual Auto Reliability Survey.

Tesla's new Model X crossover — and its signature falcon-wing doors — weighed heavily on the decision.

"The Model X launched with abundant problems, including frequent malfunctions of the falcon-wing doors, water leaks, and infotainment and climate-control system problems," noted a release from Consumer Reports."

In a comment to CNBC, Consumer Reports' Director of Automotive Testing Jake Fisher said, "The Model X out of the gate is very problematic. A lot of the problems have to do with the complex doors. The falcon-wing doors are kind of an accident waiting to happen."

A Tesla representative sent a comment to CNBC, saying the company is "committed to making the world's most reliable cars.The amount of issues we've addressed with Model X has fallen by 92% in the last 12 months, a reflection of our ability to make continuous improvements and react quickly. This commitment is one of the reasons why Tesla won AutoPacific's highest vehicle satisfaction award in 2016."

Tesla has earned praised from Consumer Reports before. One version of the Model S, the P85D, earned the highest score possible, performing better on the group's tests than any other car before it. Even at that time, however, Consumer Reports expressed concerns about the Model S's reliability.

"What seems to hurt Tesla is just this obsession with adding these surprise and delight features," Fisher said, in an interview with CNBC. While the Model S and the Model X are built on the same platform, the Model X has so much more "technology, and gizmos and mechanisms and power equipment" that raised red flags, he said.

However, the Model S gained this year, improving to an average reliability rating, and earning Consumer Reports' recommendation.

—CNBC's Phil LeBeau contributed to this report