The issue resides within PhysX, and there's no straightforward way to fix it on our end. Here are a couple of notes from the PhysX team that could help you:
If the connection was between two heightfields, there is a flag to disable collisions between the silhouette edges (eNO_BOUNDARY_EDGES). This is not supported with PxTriangleMesh officially, but it is fairly painless to hack in similar behaviour for silhouette edges with meshes.
In an example with a sphere rolling down 2 box geometries, there isn't an easy code fix for this when dealing with box primitives. The collision detection is producing a local MTD for each shape pair and this is the 'correct results' for the problem it is trying to find an answer to. A welded/no-boundary mesh shouldn't produce a little bump.
There are a few other options:
• Contact modification
• Manually create collision geometry for the environment as a single mesh (no seams)
• Write some welding code that welds all the collision geometries into a single mesh
A user has reported a physics regression from 4.19 to 4.20 where attempting to roll a static mesh down a slope made of multiple meshes no longer results in a smooth roll. The static mesh will skip as though it is hitting a hump at the junctions between meshes.
Regression?: No
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-62291 in the post.