This was the problem. Hammer spring was too long preventing the hammer from locking. Thanks!It's hard to tell without looking at it. But, sometimes lighter weight springs are longer than the stock springs. Is your one of your new springs compressing and... (I think the term is "stacking up"?) and running out of room to compress any further?
Also, if anyone has filed an angle on the sear notch on the hammer or got silly with the trigger, there may not be enough pressure on the engagement to prevent the contact points from sliding off of each other.