Thanks for the additional thoughts.
Let me clarify the current and only issue is that about 50% of the time I attempt go safe after firing, it won't engage. If I pull the trigger, it fires and then I can switch to safe.
Trigger: AR-15 FIRE CONTROL MODULE TRIGGERS DROP IN
J P ENTERPRISES AR-15 FIRE CONTROL MODULE TRIGGERS DROP IN | Brownells
"Each JP Enterprises’ Fire Control Module drop-in trigger includes JP Anti-Walk Pins that remove all slop movement of fire control components for solid reliable function, and a JP reversible, ambidextrous safety selector which has a unique drum design that ensures perfect safety function"
Anti-walk pins are part of this trigger, not an add on. I have about 500 rounds through the trigger and never had this issue until today. So, I'm thinking things may have loosened up on the trigger install. It is a drop in trigger, so there isn't the same type of assembly as with a traditional trigger.
Yes, this is the Geissele buffer made for the spring. My understanding is that a heavier buffer is recommended for shorter barrel length. This is a mid-length gas system. When I previously ran the Geissele buffer with their additional weight to make it H2 with the 12.5 barrel, the issue there was occasional fail to fire. My assumption was H2 and heavier spring was too much, so switched back to the Geissele buffer at H1 weight.
I'm going to re-install the trigger and will then test it out. I'll bring standard spring+buffer and another upper to test.