hexahedron does not work like that, you need to decompose your geometry into blocks, similar to blockmesh, so normal that it fails.
body fitting I don’t have a lot of experience, but in principle it is similar to snappy so it depends a lot in your background mesh (its parameters)
netgen, that I think is where you get in the 99% stuck, you probably have really small edge, in your step file, and that’s where netgen takes way too much time as it depends on the size of the edges, and as you have a reaaaally small edge it will take really small dimensions. try, netgen 3D + netgen 2D + wire discretisation with minimum length size, this will give you a better solution I think.
you can also use salome in convination with SHM have a look at this tutorial https://www.youtube.com/watch?v=BRCqu_Nyhhw&list=PLZDUQMOoipL6imsL2HLeLWb6OZaMOHiST&index=13
also for the small edges, check in geom/repaire/geometry check (I am saying the name out of my memory could be different) it might tell you that you have some problems on it.
hope it helps.
regards