Have you been editing the navmesh in Solitude? You might need to check and be sure you haven't ended up with some of the stupid duplication issues that are cropping up. I just had to hack off one that got me when the CK generated a 02xxxxxx form ID for a vanilla navmesh I had to repair because it's part of my cell, and another where it swapped the form ID out on a new section of navmesh I made and caused a vanilla one to delete itself.
All correctable, but it's a pain in the ass to deal with.
Your 3 errors at the end of your link:
1. The Solutide -14,26 one indicates you possibly have a deleted vanilla navmesh, or what I described, one you edited that's generated a 01 or 02 indexed duplicate.
2. That one is a busted vanilla navmesh that you probably never touched yourself but shows up now because you finalized a change which touched that cell. A highly irritating problem, and SolitudeWorld is actually loaded with these, so it's errors in Bethesda's own navmeshes basically that you now have to fix to get rid of the errors.
3. Everyone gets that one. Skyrim.esm has a broken one that hasn't been fixed and probably won't be because they're not going to update that file directly.