Hello, recently after creating a spiral pathway that leads upwards I ran into an issue where there are invisible parts that have collision on and prevent me from walking correctly and instead makes it look like I am walking on the air.
You could try turning the collision of the mesh off.
Then you use normal parts with invisibility = 1, and fill in where the parts your character is supposed to step are.
Or you could break up your spiral stairs into smaller parts. Make sure to read above on the Collision Fidelity post ^