The WS-15 were largely related to blades overheating at top speeds. There have now been successful ground tests and trial flights of the corrected WS-15.
China has needed the more powerful WS-15 for a domestically produced engine for the J-20. Previously they either used underpowered engines or older Russian engines. Russian engines have been a generation behind US engines and the Chinese were only getting inferior Russian engines.
China expects the US to deploy between 200 and 300 F-35s in Asia by 2025. China wants at least 200 J-20s. China could produce 500 J-20B, more than the future total number of other fifth-generation fighter jets in Asia-Pacific.
In April 2018, it was reported that Chengdu Aerospace Corporation, was set to open a fourth production line for the stealth fighter in 2019.
China has produced 8 prototypes and 20+ initial production fighters that using stop-gap engines.
The prototype is believed to be initially powered by WS-10 or the Russian AL-31F engines. The WS-15 will take the J-20 to a higher performance level and enable it to supercruise. The LRIP model is equipped with two WS-10B engines, an improved model based on the engine equipped on J-10.
The WS-15 thrust target was reported as 180 kilonewtons (40,000 lbf) in 2012. There are some claims that the WS-15 has reached a higher thrust level than the current F135.
The F119 engine derivative, the F135, produces 40,000 lbf (180 kN) of thrust for the Lockheed Martin F-35 Lightning II.
If the WS-15 meets design goals then J-20B’s cruise speed will be Mach 1.8 and maximum speed exceeds Mach 2.2. Those would equal the US F-22.
The US F-22 was in production for 15 years (1996-2011), at a rate of roughly two per month during peak production. China would be about 23 years behind US jet and jet engine technology. China could possibly achieve in 2019 what the US had in 1996). China stole US F22 and F35 designs and technology. Around 2030, China could have 500 J20B and 100 J20 and J20A stealth fighters. The US would have 185 F22 and perhaps 1500 F35s.