Function test your lower is pretty easy, hammer should reset with just a few pounds of pressure and the safety should work. I think the psa is a ramped bolt, so it should use standard lower parts with a different mag catch. The hybrid uppers must be used with a hybrid lower, not sure what is different.
Lube the bolt, make sure it cycles freely in the carrier and the carrier slides freely in the upper.
Check the buffer spring and buffer to make sure they are free and the right parts for a AR9 (although wrong spring and buffer would probably cause a short stroke)
If it's locking up, probably a gas/bolt issue. About the only thing you can goof up in a lower is getting the hammer spring backwards which will cause light primer strikes.
