and the main issue is limited overhaul times
....and spares. The third world is littered with derelict Russian aircraft that have been cannibalised out of existance. Botch-ups were the normal method of repair. After a few crashes involving Russian airliners the Chinese CAAC read the Riot Act and withing a few years they were all replaced by western equipment with prompt and traceable backup.
On the approach to Tianjin in the late 90s you could see the ex-Aeroflot 154s being stripped for spares for Chinese 154s.