It’s a combo of both. I bought a set of 4 10AN 90* fittings and the 4 straight fittings on eBay for like $25 or so and ended up trashing them after trying to get them to take the cheap (10 ft for $15, again on eBay) braided hose. I tightened the crap out of them in the hose ends and to where they attach to the straight fittings as well.
Once I removed the whole set up, and nutted up and paid for good kit; I found that once I removed all the cheap faulty stuff the threads on the straight fittings were chipped here and there and the hose loosely fit the 90* fittings, hence my leaks.
I will also add for the threads I used the ARP thread sealer on the Fragola fittings. And a little goes a long way:
Part/serial 100-9904 is what you would use in your search on Amazon or EBay.