Go from simple to difficult.
Give it a good cleaning, examine the receiver and it's internal parts for anyting that might be obvious, try a better grade of ammo, use a different magazine, and see what happens. If the problem continues, it's time to look at the extractor and other components in the receiver. One thing at a time...
If your receiver has rivets going through it, then it's probably stamped. Vector shows a stamped receiver in their photo.
As for price, I can't say. I bought my AK from Arsenal Arms, made in the USA. It's milled steel and built like a bull dog. Clean finish and accurate. To date I put thousands of rounds through it with one jam. It empties a 30 round mag in seconds. I paid $650. It's the SAM 7.
The other option is to bring it back since you only had it one day.