Sphynx_V1 - Hammer super stiff?

Does anyone have any advice on fixing an incredibly stiff hammer on a Sphynx_V1 frame? All other parts installed fine, and the hammer isn't stiff until I install the lanyard onto the spring. That installation is super stiff and requires me to lever the frame against a table to get the lanyard lined up with the pin hole. Any advice from people that have built these? I took a round file to the hole where the lanyard goes in to ensure it moves smooth without any binding, but still no success. Everything else appears to function as expected.