Try "Boogs" solution at the range with the mags that fail to lock slide back on last round. If it works, then its a spring problem. JMO
I suggested on another 380 EZ post, that with all the members on this forum that someone could try a spring from another 380- 8 round mag from some other gun manufacturer to see if it resolved this problem If someone does, PLEASE list the gun you got it from!

Be SAFE and Shoot Often!