Like my other thread, this is someone else's dirty mod with some accidental/old edits. I'm trying to clean this one because of issues with other mods I have; it changing navmeshes in areas it doesn't actually add content to (Ivarstead and Riverwood)

When I toggle the ignore flag on the offending NAVM entries in Data>Details, upon loading the plugin to save the changes, it force-closes the CS. Am I doing something wrong?

Any time you do that with navmeshes, you should remove the NAVI record along with it. Otherwise it contains invalid data and the CK tends not to know what to do with itself. Once you've got the plugin loaded after doing that, save it again so the NAVI gets regenerated with the proper data.

Right, thanks. Deleting the NAVI record won't mess with any other new navmeshes that haven't had the ignore flag toggled though right?

"Ignore" flag just means the CK will remove the override upon save/close. Recreation of NAVI shouldn't be affected as those NAVMs will be removed and shouldn't be included.

Keep in mind that while those areas may not be actually altered by the mod in question, they may be cells adjacent to an altered area. If this is the case, and you delete those adjacent cells' navMesh data (NAVMs and NVMIs), you may experience issues with AI not being able to properly enter/exit the modded area; unless it's an unchanged Vanilla area.. in which case the Vanilla navMesh should still be in place and working properly. (different formID navMeshes seem to be overlaid on top of each other, not dynamically 'combined')

[EDIT: because of the cell-border mergers.... I don't know why I didn't mention that above heheh]