On a Paper, Change the Methodology or Report in Results Section?
This should be worked out with your advisor. If it were me (as advisor), I'd suggest that you explain the original methodology and show how your work implies that it fails. That is a valid research outcome. Then, show how a modification of it would work and why. How is it that the &quot;technical details&quot; make a difference.
But if you change the methodology and just pretend that it didn't happen, you are losing an opportunity to extend knowledge. A proof or demonstration of why something doesn't work can be just as valuable as one that it does. Perhaps even more so in a case like this. If your thesis gives insight into a problem, or better, a class of problems, you have done well, no matter the outcome.