Went off the rails can mean several different things.
if it went off the rails because issues with program management by Shenyang or deficiencies of the technical team, then it would seem the optimal solution is to bring in a better team, not restart almost from scratch.
if it went off the rail because basic unsuitability of the airframe, I will have to ask what makes it less suited than the J-20?
also, I find it difficult to believe that, when engine design is the one area where Chinese aviation industry is particukarly weak, the Chinese navy would voluntarily accept a long delay in its premier carrier aircraft if the end result is a single engine aircraft replacing twin engined aircraft for is main shipboard aviation role.
Come on ... to speculate why it went of is the completely wrong conclusion. We have several rumours, reports and even confirmation from AVIC/SAC, that all sums up to the single conclusion, that the FC-31 was chosen to develop the PLAN's next-generation carrier-borne fighter. IMO we can take this for granted!
And even if there have been reports during the last 6 years, that CAC proposed a J-20-based design or even a new single engined type, these came all to and end the more the SAC-related reports shifted from rumours, reports to finally confirmation.
As such - and I can only agree with
@Bltizo - it makes no sense that there si now again an open competition, a fly-off between two different designs ... and in fact if true this would ruin all my believing in PLA-watching.
So in consequence and even don't know the source nor do I want to question
@huitong's words, I would rate these latest rumours simply as unlikely rumours (at least as long as we don't know the source) and I'm still waiting for the public debut of the J-35 (?) as the PLAN's sole next-generation carrier-borne fighter.
Just my 2 Cents.