A manned Soyuz rocket suffered a partial loss of pressure as it returned to Earth earlier this year, Russia's space agency said Wednesday, in the latest glitch to hit the country's space industry.
The incident during a voyage back from the International Space Station in April did not put the crew's life in danger, the Roscosmos space agency said in a statement.
"As the Soyuz MS-02 (space capsule) descended from orbit, it experienced a slight loss of pressure during the opening of its main parachute," Roscosmos said.
"This in no way endangered the well-being of the crew as they were wearing sealed space suits."
Cosmonauts Sergei Ryzhikov and Andrey Borisenko were in the spacecraft with NASA astronaut Shane Kimbrough, according to a NASA report at the time.
The problem came to light during a meeting of NASA's ISS Advisory Committee this week and was reported by the industry journal Space News.
"This situation was investigated with the cooperation of NASA. After that, successful launches and landings of the capsule were carried out," Roscosmos general director Igor Komarov said in the statement.
But Space News said the loss of pressure was "one of a series of events that have raised questions about the reliability of Russian vehicles supporting the ISS".
Most of those incidents have involved unmanned spacecraft, though in 2015 a solar array -- a type of power supply that captures energy from the sun -- failed to deploy on time during a manned Soyuz docking.
In December last year, an unmanned Progress ship carrying supplies lost contact with Earth minutes after blast-off and burnt up in the atmosphere over Siberia.
A commission appointed to investigate the malfunction concluded it was caused by the break-up of the Soyuz third stage rocket engine, either due to "foreign materials" getting inside or an assembly fault.
In April 2015, a failed Progress launch was also blamed on a problem with the Soyuz rocket, a space workhorse dating back to the Cold War-era.
Russia, which is currently the only country executing manned space flights to the ISS, put all space travel on hold for nearly three months.
A group of astronauts had to spend an extra month on the station.
In June this year one man died and another was hospitalised after they were caught in a fire on the steppes of Kazakhstan triggered by falling debris from a Russian space launch at the Baikonur cosmodrome.
Corruption scandals have also plagued the new Vostochny spaceport in Russia's far east.
