Problem with a asset navmesh collision

I am quite new to use UE5, and I use UE5 for learning purposely. So when I thought out that I wanna create a certain level, I looked thro the UE Marketplace to find some assets. Download the assets that I wanna use, and then put them on my level.

While I have been working on that level, I have only used the default camera to move around the scene when I press on the “Play” button. Everything looked great. But that was until I experimented to add First Person or Third person player model(the mannequins).
So when I pressed start and started to walk on the map, I have noticed that the asset that I am using on the level, it’s ground navmesh collision is very weird.
When I mean weird, then I mean like, when I start, it looks like the player is standing normally on the ground. But if it happens that I walk along on the(for example) the road asset, then somehow the camera moves a bit up, then the whole player model moves up and walks on air, above the ground. While I am still walking forward, there is a part of the road that makes the player model to fall off to the side.

I have also tried to move the player spawn further up on this road and try walk downwards instead. But when I do that, same thing happens, but instead of sliding of to the side of the road, I somehow slides into the road and get stuck from there. I have not touched any of the model/assets settings at all.

So my question is: Is there a way to fix it in the Unreal Editor? So that I somehow can fix it from my end. Or do I have to wait and report this to the UE Market people about this stuff for this asset?

Picture(After when I walk forward on the road from player spawn):

Picture 2(When I walk further on the road):

Picture 3(When I walk downwards from the road after moving the player spawn):