The 2015 incident is written about in detail here:
https://airlinegeeks.com/2018/02/11/...t-near-moscow/
2015 Controversy
Until Sunday’s accident, Saratov Airlines has had a mostly unblemished safety record. One exception is an unusual incident which occurred on Jul. 19 of 2015, where a surprise inspection by the Russian Federal Air Transport Agency found ‘a violation of Russian Federal Aviation Regulations concerning the presence of persons other than flight crew in the cockpit during operations.’
The subsequent investigation found that on a flight from Saratov Tsentralny (RTW) to Antalya, Turkey, a ‘close relative’ of the airline’s general director was found to be present on the flight-deck without official authorization.
As a result of this incursion, the airline was banned from operating international flights. At the time, foreign destinations included Ukraine, Azerbaijan, and Montenegro. As mentioned above, only international routes to Armenia and Georgia currently operate. In response, the airline took action against a number of employees, as well as introducing a number of policy changes to ensure no such errors would occur again.
And from the time:
Saratov Airlines loses its international business over security violation - Russian aviation news
Commenting on the implicit danger of letting an outsider inside the cockpit, Rosaviacia reminded another incident, that resulted in a crash that killed 75 people aboard an Aeroflot Airbus A310 aircraft in March 1994. The cause of the accident was a pilot’s decision to let his children into the cockpit and allow them to take control of the aircraft.
Which... well, it's quite a big jump from 'letting someone unauthorised onto the flight deck' to 'handing over control and walking away', but whatever.