Are you on Discord or can I DM you somehow? (Want to send you some confidential materials of our map)
Nice to hear you are investigating the issue!
I have tried moving around meshes and npcs but nothing seems to fix it. I even made a script that teleportes the npcs and waypoints individually around by small increments testing thousands of positions, testing if any combination of global playspace location would work, nothing changed.
I was able to determine, using the NavMesh Debug Tool, that the NavMesh generation is becoming corrupted and is no longer being generated correctly.
I have forwarded two short videos to you that show the exact same location. In one video, the NavMesh is generated correctly, while in the other, it is generated incorrectly.
You should receive the clips shortly.
Can confirm this, just tested it again
Hello, after investigation, it seems that the problem comes from the collidable mesh components in your NPC prefabs (especially the text mesh). Those meshes are moving a lot and dirtying many navmesh cells. Unticking collideable/queryable in the prefabs for the static meshes that donât need collisions will help a lot.
Thank you! We will check that asap!
UPDATE
It seems that unchecking the Collidable and Queryable settings on the mesh components used for our NPC text has actually resolved the issue in our case.
Iâll be doing more testing today to verify this 100%.
Itâs worth noting, however, that everything worked correctly with these settings enabled before the 41.00 update. The issue only started occurring after that update.
Hey,
I have tried disabling collisions, queryables, which affects navigation⌠and tested all types of different settings for all the static meshes in the navigatable area of the npcs, but the problem persists. I have even tried reverting to older versions through revision control, which I am certain did not have any of these struggles before the v41.00 update, but they still donât work either. Also, I tried removing a bunch of the meshes and devices that were in the navigatable area, and that didnât help either.
I still believe that something about the navmesh generation is broken since this update (could be wrong, but thatâs what all my testing points toward).
The behaviour also seems random, sometimes the NPC navigation works (a little bit), and most of the time it does not work at all.
I have tested both in edit session and private playtest, none work.
Also, the NPCs in my already published version of the map that I published pre v41.00 and havenât updated since, also stopped working (map code: 3278-3366-0706)
UPDATE :
Like @ToolFNC posted in this thread, I also discovered that disabling QUERYABLE on a mesh component inside one of my prefabs, that also had a keyframe movement component inside (playing a small, simple shrinking & growing effect), seemed to solve the issue.
However, this âshouldnâtâ be a problem since this prefab doesnât even exist in my published version of my map, which also doesnât work. Therefore, I still believe something is broken with the nav mesh.
Your van is dirtying the navmesh when it moves and when it wobbles because it is queryable
We would need to add a way to keep it queryable without dirtying the navmesh
Quick update, before 41.00, static meshes were not dirtying the navmesh when they were moving; this is now fixed, but this can lead to performance issues. We are investigating a few solutions.
Hi! Is the fix already live? Or will this come with the next update?
The fix for static meshes not dirtying the navmesh is live in 41.00. The problem is that characters or vehicles made with prefabs and animated per frame are causing issues because they dirty the navmesh each frame. The best way to fix this, when possible, is to remove queryable/collidable on the meshes.
Alright, thanks! 
Okay the latter seems like a workaround for certain cases, but when will the proper patch for the problem be deployed? v41.10?
Yes, we are aiming for that (the fix would be to not update the navmesh until the entity stops moving)
Iâm lacking some experience in the navmesh field so the following question is just for my understanding. If an npc entity moves, then it moves based on the nav mesh surrounding it, but is the navmesh already available for all the areas it could be moving onto (if itâs static ground), or will the npc eventually hit nav mesh border, stop, cause the navmesh to update and continue moving again? 
Yes, disabling queryable and collisions on all the prefabs I could seems to have solved most of the nav issues for me. However, it is still buggy at random sometimes. Hopefully the next patch will reolve this
FORT-1113926 is âClosedâ as âFixedâ. The issue will be addressed in 41.20.