So I got 3 M14s from Marstar. 1 for me and 2 for other people. 2 disassembly easily but the third one will not. The trigger assembly is impossible to take out. It looked like it was slightly covered by the stock so I took off a bit of the wood to uncover it. Still won't come out. Any possible ideas why it won't come out? Is it defective? Will I have to send it back?