I deleted the vanilla navmesh in the interior cell, the Four Shields Tavern in Dragonbridge. I set up my new navmesh and finalized it and no problem. Went in game to check it out and saw that NPCs were trying to exit through a door that have been moved now to the other side of the room. Then the game crashed.

I went back into CK and after loading saw that the original navmesh had reappeared along with my new one and now I have a double nav mesh. So I deleted it all and started again.....went ingame to check and the same problem with NPCs. Reloaded the CK and it is the same thing, a double navmesh with CK warnings about refinalizing the navmesh.

I have no idea what to do at this point.....if anyone has any ideas I would be very grateful.

First rule of navmeshing: Never delete a vanilla navmesh from a cell.

You'll need to remove the navmesh you laid down, then make sure the vanilla one is present. Modify that to suit the cell. You may need to use the CK details screen to remove the record saying that navmesh was deleted before it can be brought back.

Your own navmesh for that cell should have a form ID starting with 01 or 02, use the cell window to delete them from the mod. Make sure the CK will save the results, and once it does, you should be back in business.

Ah okay, thanks very much!

your problem here is obviously you didn't finalize your new navmesh.
if there's a door, there's an according door-triangle on the navmesh (green after finalizing), which is assigned to the navmesh when you finalize.
npc's will assume this triangle as the door, not the actual door-item, so without finalizing, if they try to get out, the only door-info they'll find is on the old, deleted navmesh.
that's why your game crashes, because they try to move onto a navmesh that's no longer there, and that's why the old nm doesn't get deleted, because the door-reference from whatever is on that door's 'other side' still points to the door-triangle on this nm.

apart from that, i strongly second everything arthmoor said about not deleting navmeshes (though for interior nm's with no doors or any other nm's bordering it, it might be more or less safe, but that's certainly quite some ifs to many for any kind of recommendation

Unfortunately it wasn't as simple as that. I did finalize and the green triangles were correct by each door. But thankyou anyway.

So I deleted my new navmesh and undeleted the vanilla one, then modified the vanilla one. Now there is no error when loading in the CK and I have watched NPCs walking up and down my stairs and around. So all seems fixed. Except that Faida will rent me the room, then tell me she will show me to it, but she stops at a certain place only a few paces away from her position by the bar. She won't move beyond that point. Even though I have seen her move beyond it when doing her sandbox AI.

Then after a while she 'teleports' upstairs to the room and completes her 'let me know if you need anything else' then teleports back downstairs. Her script and properties are fine, her AI is correct....I have no idea what could be causing this, especially after seeing other NPCs walk upstairs with no problems.

Anyone got any ideas? Maybe my save game? But then I have used a few to test. I even took Lydia and she walked up and downstairs with no problem.

Normally that behavior means the AI has encountered something blocking their path. They will wait for the blockage to be cleared, but if it takes too long, the game will teleport them past the blockage.

If that helps any.

if this faida is a shopkeeper, she'd probably be bound to her shop marker during opening times. should run an own package

I have an exterior navmesh that the CK complains everytime I start it that the navmesh needs to be finalized. I do not, however, see a second navmesh, and no matter how many times I finalize the navmesh in question, the CK complains about it on every load.

Any Ideas?

BTW, its the Levelers Tower mod, and the navmesh is the one surrounding the tower.

What I would really like to do is reset all the exterior navmeshes to vanilla and just leave them alone... My attempts with TESSnip usually fail as I don't really know what should be ignored...

That error means you have a deleted NavMesh form in your mod. Go into the Details for your plugin and search for any NAVM records that are flagged as deleted and Ignore-flag them. This will restore the deleted NavMesh, after which you go to the cell which has doubled NavMeshes, select the unedited NavMesh, and sink it into the ground far enough so that it will never be used.

When dealing with exterior navmeshes, you can't really avoid the need to directly edit them. If all you need to do is move a few triangles (or delete a few triangles) you can even get away with not finalizing the navmesh again. If you need a door, you will need to finalize that if you expect NPCs of any type to be able to use them, including followers.

So what you'll need to do in this case is undelete any deleted navmeshes, then go into the affected cells and find the ones that start with your mod index (01 or 02, depending) and use the cell window to delete those. Then save so that the NAVI record is updated properly.

TESSnip worked wonders. Thank you all for the tips!

I actually did NOT delete the navmesh. Apparently, when you Optimize, it gives the navmesh a new formID. And thus, there was no 'deleted' navmesh to recover (ignore the delete) so I used TESSnip and after some trial and error, I managed to remove the correct records and the edits are now gone from my mod.

I wanted to remove all the 'edits' to the exterior cells in the cells around my tower entrance cell. I can live with my one exterior cell being edited.

In case you are unaware, the current release version of TESVSnip contains dangerous bugs regarding truncation of compressed records, and this includes CELL and NAVM records. I can't speak for the dev version, but if you are using the release version on Nexus, very serious damage can be done to your mod by using TESVSnip on it, damage the Creation Kit cannot undo.

Since I removed the entire NAVM record and its subrecords, should not be a problem.
The CK complained about the header count, corrected it, and seems fine with my edits otherwise.

That doesn't matter, because Snip still has to save the rest of the file in order to do that. It doesn't process any compressed records properly, which includes cells in both the exteriors and interiors, along with landscaping, navmesh, and NPC data.

You may not notice it right away, but eventually someone will come along asking about "blue voids" in various interior cells that your mod doesn't even touch. That's the kind of thing the corruption causes to happen, and it gets worse the more times you use Snip to edit the mod.

The part that svcks about this is that by the time you realize what's happened, the mod is no longer salvageable. I ended up having to rebuild 5 out of 6 of mine because of this issue.