Bare with me a sec.
I've built several AR's from scratch and all worked with no issues and continue to run great. I've taken apart numerous rifles, shotguns, and handguns and swapped parts out of all kinds of firearms. Everything always went back together with little to no issues and functioned as it should. Enter my newly acquired SCT-19...
I had some time to work on it after working late today. The slide went together just fine. The frame, I thought, went together just fine. Please keep in mind this is the first time I've had any time to work on it, so I just wanted a test fit/function test. I haven't prepped any of the internals yet; i.e. polishing and a few other things I need to do before assembly.
The trigger doesn't feel right at all and I can reset it just by pulling the trigger forward. Racking the slide doesn't reset the trigger, but when I try to take the slide off, the trigger resets. The slide doesn't come all the way back to use the slide release to lock the slide back. It's almost there, but not quite. I finally got the slide off and stripped it. I started stripping the frame, but the trigger pin won't budge at all. It went in super smooth with no issues, but it will not come out. HELP!!!
First question, are you using OEM internals? Ok ummmm well obviously (well maybe lol) it's not resetting because it's not fully cycling ("...the slide doesn't come all the way back..."). Not sure why that would happen but let's tackle some other stuff first. Trigger pin is probably being held by the slide lock/release lever (hope you're trying to remove it from left to right). Trigger issues are usually connector related. Does it feel mushy when pulling? Check to make sure the connector isn't pushed in the trigger housing too far or not far enough. Meaning the angle in which it sits in relation to the housing (I'll post a pic shortly unless Hawkeye beats me too it). Is the trigger housing seated properly? Also the sharks fin could be dragging the bottom of the slide. What's you spacing between the slide and frame look like? Post up some pics of all mentioned and maybe we'll see something.