Found a parts diagram.
https://www.americanrifleman.org/con...n-disassembly/
The Mainspring Auxiliary Lever (Part 39) is a Rebound Lever which acts of pressure from the lower leg of the Mainspring (Part 38). Without seeing the fyrearm and examining it, it could be dirty (congealed oil & dirt can lock up an action), the Pawl/Hand (Part 40) getting hung up. The Sear (Part 29) could be refusing to let the trigger from slipping past it and returning to its position of rest.