I stimulated a section of roller chain under the stress of 100N. The resolver sorted the length of its stretch is 0.00246mm. And then I created another very similar analysis. Set the roller chain is stretched to 0.00246mm. However, the calculation result shows it only need 74Newton pull force to stretch 0.00246mm.
post the details of your analysis setup
maybe a picture of your model
and your hand calculations
this sounds like a classic example of setup doesn't match calculations