With mesh (stairs) following the curve path. Few stairs are in align rest as it goes up the stairs bending. Rotation scale applied. Tilt is also 0. Whats going wrong. Any suggestion or help Thanks.
The Tilt of the vertices are at 0° (3D View > N panel) so it's not the problem. You need to select the curve and choose Twist Method > Z-Up. That said the object is still not completely vertical. If it's too noticeable you need to switch to the Instancing method: Give the Array and Curve modifier to a vertex instead of your object, enable the Instancing > Vertex of this vertex, and parent your object to the vertex.