Reproduce:
1. Download this mod's main file :https://www.nexusmods.com/skyrimspecialedition/mods/9666?tab=files&BH=38
2. Install it anyway(though it's fomod it only contains one esp)
3. Quick auto clean it
Then sseedit will log 34 itms are removed. There are a lot navmesh like NAVM:001020DA NAVM:000FEDD9 from the mrissi mod being removed.
While you check these navmesh using uncleaned esp by sseedit, you will find they are colored as yellow and some data in it is actually different from skyrim.esm. 2 or 3 Triangles (and only one or two hex number in them are different), edge links are different and in yellow color.
I don't know much about how navmesh works. The question is, is this the correct way to clean it? They seem to be edited by the mod author. Or these should just be regarded as itm?