After applying a Linear Stair brush to the editor and creating a Static Mesh from that brush, then setting its Collision Preset to BlockAll, the third person character is not able to walk up the stair and walks through it instead. The collision on the stair does not work.
Results: The character walks right through the stairs
Expected Results: For the character to be able to walk up the stairs with Collision Preset set to BloackAll.
After converting the BSP to a static mesh open the resulting asset, Under Collision, Collision Complexity Set it to Use Complex as simple.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-54212 in the post.