Raycast detect gaps in UCX collision

For a racing game I’ve created a race track in blender using the curve and array modifier. I’ve also created cube collision objects (UCX) which I want to import in UE4. I applied every modifier before exporting and made sure, that there are no gaps in the mesh, using merge by distance. The model in Blender looks like this:

I manage to import it to UE4, but when playtesting, it seems like the kart detect little gaps in the UCX, making it lift upwards. The kart uses 4 down raycasts for detecting the ground. please take a look at this video:
https://streamable.com/g6eps1.

The Collision in UE4 looks like this:

What’s the problem here, and how can I fix it?