Gary,
I never disassembled a Parker Repro so I cannot give you a good answer. Since it is a faithful reproduction of a Parker it should be the same. Someone else will soon respond...
For your single trigger, try a good cleaning first. If that doesn't cure the problem send it to Mark Beasland of Mark's Born Again Bird Guns. Email: mark@mbabllc.com ~ (866) 622-2486
http://www.mbabllc.com
Mark is in Wisconson but I do not know which town.
Mark