He drilled an extra hole in the body of the device and sealed it with glue, not telling anyone about it.
The air leak on the ISS happened due to a marriage in the production of the Soyuz MS-09 spacecraft. The employee of RSC Energia made an extra hole in the hull and concealed it with glue, which dried in two months. This was reported by RIA Novosti referring to its own sources in the space industry.
One of the interlocutors of the publication said that the problem appeared on the Earth during the assembly of the Union. According to him, the responsible has already been established. Another source specified that when the employee realized his mistake, he closed the hole with special glue. Because of this, the problem was not detected during the inspection of the ship for leaks.
It [the crack] did not make itself felt the first two months of the orbital flight.
However, in the future, the glue dried and was squeezed out by opening the hole.
Sources of the publication also reported that the RSC Energia began an internal investigation of the incident. The Special Commission will hold its first meeting on September 3.
The scientific director of the Space Policy Institute Ivan Moiseev, in a conversation with RIA Novosti, expressed confidence that the cause of air leakage to the ISS was just a manufacturing marriage in the assembly of the Union. According to him, collisions with micrometeorites occur quite often, but in the history there were no cases when it caused the depressurization of the spacecraft or station module in orbit.
The air leak on the ISS occurred on the night of August 30, 2018. First, the crew of the station eliminated the problem with a special adhesive tape, but it was not enough and the pressure continued to fall. The astronauts compensated for the air leakage with Progress cylinders, they had to seal the hole twice – an additional patch was applied to the installed seal.