Literally have no idea where you got J-20 has production issues. Apart from Inst (I don't even recall him speculating this), I don't think anyone thinks that J-20 has production issue where every indicator and leak suggest that production is at least as fast as J-10C.
I can only agree, even more since the J-20 is not - as we say in Germany - eine "eierlegende Wollmilchsau" (a pig that lays eggs, gives milk and wool)
! There are roles, which does not require a large twin-engined stealth fighter, there are roles, for which the J-20 eventually is not ideally suited, the J-20 is too large, too heavy, too expensive to replace all types in PLAAF service and even more it has an important industrial-political role: the keep SAC in the fighter business.
However - and please don't rate this as an issue - I don't think that the J-20 "production is at least as fast as J-10C"! We have seen 28 J-10Cs and "only" 7 J-20As with three more allegedly on the other side of the hangars left (making altogether 10), so that i expect the current production rate roughly 1/2 or even only 1/3 of the J-10's rate. But that is only my guess.