The upper was built by a local who builds AR's and the lower is built on an Anderson frame, also built by a local guy.
Thats usually a clue for questionable work. Let someone who knows what they are doing (a gunsmith, not some random guy slapping AR's together with cheap parts) replace your trigger or install it correctly.
Its very easy to do if you want to tackle it yourself. Watch the video below.
http://www.brownells.com/GunTech/Brownells-How-to-Install-An-AR-15-M16-Trigger/detail.htm?lid=16175
