Russian officials believe that the defective component was damaged during assembly.
During the aborted launch October 11, the crew capusle carrying NASA astronaut Nick Hague and Russian cosmonaut Alexey Ovchinin was able to safely separate from the rocket after getting a warning signal during separation, firing engines to gain distance from the booster, according to NASA spokesperson Reid Weisman.
Roscosmos officials explained that a malfunctioning sensor led to an issue with the separation between the two rocket stages, causing one piece of the rocket to fail to separate fully, sending the rocket into a spin and prompting the instant abort.
The incident, on 11 October, was the first serious launch problem by a manned Soyuz space mission since 1983.
Roscosmos is due to hold a press conference Thursday to further detail the findings of the accident probe.
Russian space officials plan to conduct two other unmanned Soyuz launches before launching a crew to the space station. Secondly, it's great to see that the Soyuz rocket's safety abort system works so well, and it should be a great comfort to space travelers who will soon be riding the hardware to space once more. The current space station crew - made up of NASA's Serena Aunon-Chancellor, Russian Sergei Prokopyev and German Alexander Gerst - was scheduled to return to Earth in December after a six-month mission but will have to stay there for at least an extra week or two to ensure a smooth carry-over before the new crew arrives in early December.
Because of the sensor failure, a side block of the first rocket stage separated incorrectly, impacting the second-stage fuel tank, which then exploded.
Despite their dramatic descent and landing, both men were recovered unharmed, the space agencies said.
"The reason found by the commission (investigating the accident) was the abnormal operation of a sensor that signals the separation of the first and second stages", Krikalyov said at a space industry event in Moscow.
Russian rockets are manufactured in Russia but the final assembly takes place at the Russia-leased Baikonur cosmodrome.
They had initially been scheduled to land on December 13 after their stint on the ISS, a joint project of the space agencies of America, Europe, Russia, Japan and Canada.