A few months ago while I was plinking, that pin and bearing fell out of my scar.
this bearing is very important. if you fire the gun without the bearing, you will damage the hammer and scrape up the big grey bolt carrier. I used crazy glue and locktite to keep the pin in place but it didn`t work. After firing a few rounds of full auto the pin comes loose again. As a temporary fix, I went to a rc hobby store and bought a replacement bearing. the pin fits so snuggly into the bearing that it can no longer fall out. But this is only a temporary fix. I`m going to replace the hammer piece itseft from ra-tech. hopefully that will help.
edit: This will probably not fix your trigger mech problem. your going to have to open up your trigger mech box( very carefully in a tupperware box so ball bearings don`t fly away on you) I bet the springs that resist the hammer are bent or broken, or the firing pin is broken or something.
If you don`t know what your doing. Watch this video:
YouTube - WE-Tech SCAR-L: Lower Receiver Takedown
And then watch this one:
YouTube - WE-Tech SCAR-L: Trigger Assembly Takedown (Part #93)