There seem to be a lot of issues with the Russian aviation export business, they recently lost a tender to supply India with Mig-35's mostly due to issues with the sharing of technology, the poor performance of the engines and radar systems and the supply chain demands that the Russian's had put in place in their tender to compete.
However the Russians seem to have the Chinese over a barrel, the Chinese J-10 fighter
Was supposed to be a completely Chinese built endeavor, but it sounds like the Chinese are having trouble "designing" (which means that they stole the design from the Russians) and manufacture of the really complex engine and have now been forced to buy engines from the Russians.