LaZouche Custom airsoft new strip down of TM MEU 1911. - YouTube
Check this playlist for the 1911 takedown and reassemble. This guy has some tips and tricks for troubleshooting a 1911 it is a meu however on his channel somewhere he has 1 for the highcapa based pistols. I used this to do work on my meu. Hopefully after watching this you may have some more insight into the problem.
P.S
he does do a section on the takedown vid about the 3 finger spring and the sear that may help you.
Cheers,
Whiskey