Yes, China has struggled with the metallurgy necessary for advanced turbine engines. They seem to have made significant progress recently.

https://www.twz.com/air/our-best-look-yet-at-chinas-j-20a-fi...

Russia is no longer a reliable supplier. They need all the engines they can make for domestic use, including replacing war losses and building airliners to service domestic routes. Production is down because all the foreign technical experts left.