I am working on the OP as we speak.

I am convinced that Bethesda's treatment of navmeshes is poor at best. Dawnguard.esm was causing CTD's on half the map until I cleaned it with version 3.0.22. However for some reason the CTD's starting creeping into the game again. I have verified the files thus replacing the cleaned esm's. I restored the backups of the other mods I've cleaned. And I started the process over again. Not a big deal since I only had 8 dirty mods. I cleaned Update.esm first, then Dawnguard.esm followed by Hearthfires.esm. I am once again able to coc to deadcronerock01 (which as detailed in many other posts I was not able to do before cleaning) but I cannot make my way back to Lakeview Manor. The exterior grids surrounding it are causing CTD's. I am aware this isn't at all the fault of TES5Edit. I'm really just mentioning it because I'm trying to figure out how those grids became unstable again and to find out what further updates to cleaning will be done. Maybe navmesh info is stored in the save? Like ugrid settings?

Thanks for restoring the the esm files and cleaning them with the new version. I'm not sure about what World Space information would be saved into a save game.

This would be just for testing. If you already verified your cache after obtaining 3.0.23 then skip that part. If not just to be on the safe side, get all your files updated not just the esm files. Can you verify your cache, clean your esm files, only have the Bethesda files active, and go there with a new char in god mode maybe or something. What happens when you arrive? I ask because there are still going to be issues with older plugins.

Also remember to load Skyrim.esm and Update.esm, but only clean Update.esm then close TES5Edit. Then Load Skyrim.esm, Update.esm, and Dawnguard.esm, but clean only Dawnguard.esm.