Can you tell me what version of UE4 you are using where this occurs? Has this just started occurring or has it always happened with this asset? Does this only happen to the one asset? If you replace the collision with a simple box collision, does the problem persist? Can you share the asset in question with me so that I can test it personally?
It’s the first time I’ve tried building a navmesh around this asset so I’m not sure if it would have done it in previous versions.
No unfortunately it’s not just the one asset, it seems to be a semi-random selection of similar assets. They’re all from the ‘ancient worlds’ marketplace package which I bought recently. As you can see here: Screenshot - 44e30140674fcfa74d13582ad29b5c4c - Gyazo
Quite a few of these wall segments are having the same issue, though notably the two side by side to the gate are fine, and the navmesh is forming properly around them.
You can see there the simple box collision interacting with the navmesh exactly where it should, and the other one being 90 degree’s to it.
More than willing to share the asset to help figure it out, What’s the easiest way to do that?
EDIT
Further testing, any form of generated collision within UE4 seems to work fine, it seems to just be taking issue with the collision mesh the object came with by default. In the meantime I’m just using the generated collision as a work around, though the bug remains and happy to help provide things to help you find it.
Thank you for clarifying that information. I have spoken to the Marketplace content team about the pack to get more information on what may have happened. What I discovered was this is a known issue with the visualization of the NavMesh with custom mesh collision. It should not affect pathing, but just the way the it is rendered. We do have a bug report in for it and the team responsible is aware.
Please let me know if AI movement does not path through it correctly.
Unfortunately it does botch the pathing as well. When I had it just with the original collision, the AI would path around the entrance and attempt to run through the solid wall, and just run against it constantly. So the collision on the object was fine but their pathing was working as it was visualized.
I tried this with the content you described and can see this is a related issue. I entered a new jira ticket for the differences (UE-13943) and passed it to the developer in charge of navmesh generation. Please let me know if there is anything else I can do to help in the meantime.