This is the down side to taking the Chinese route.. . . It's lottery, one with lot more losers than winners.!!! . . . . The mechanicals can be tweaked and sorted to some degree but the electronics are junk in which case best starting again if want complete peace of mind/reliabilty.

Like the Old saying "can't make silk purse out of sows Ear" so advise friend not to try. Bite the bullet and re-fit with decent electronics.