Perhaps this could just be a warning to always insert your Axis' sear pin from left to right, but I was at the range last week with my .243 Winchester build when the trigger became much, much lighter. To be honest I don't remember if the change happened while I was shooting or if it came out of the case with a hair trigger, but either way I mentally compensated for the new pull and didn't think much of it. The first thing I noticed was a slamfire when I closed the bolt. It was jarring to say the least but muzzle discipline helped to prevent any disasters.

Before I disassembled the rifle, I concluded something went wrong with my trigger job. The shim I epoxied under the sear should be fine, as it's designed to be fail-safe: should it fall off the sear shelf it will result in a creepy trigger, not an unsafe one. It was possible there was some other obstruction caught under the sear though. I also considered the replacement spring may have come loose or failed in some way.

But as I'm sure you gathered from the title and first line of this post, the actual cause of the ultra-light and unsafe trigger was the sear pin. I had inadvertently inserted the sear pin right-to-left instead of the correct left-to-right. I don't know how common the problem is, but I came across this photo showing incorrect pin insertion and an inadvertently slipped sear:


(From here.)

Furthermore, my rifle is in a Boyd's Tacticool stock. I don't know if the inletting of a factory stock is closer to the pins to prevent this from happening, nor do I know if there's any part of the design that actually prevents the sear pin from walking out the other way.