Wk180 issues

Bought a KD wk180c for my first purchase and so far it's been a pile of junk. Have about 250 rounds through it with 3 different brands of 223/556, steel and brass cased, and it's FTF/FTE about 15 times now. Have 4 of the 10 round cross mags and it doesn't matter if I use those or the original 5 round mag, will eventually jam. Before I ever fired it I removed the BCG and cleaned/oiled it, the bolt moves freely and smooth. Someone said I needed to buy an upgraded ar15 extractor Spring kit? Why do I need to buy upgraded parts for a brand new rifle to work properly? Accuracy has been good that's the only positive so far.