Definitively a bug in the BVPSystem constructor from BoundaryValueDiffEq.jl
It assumes same type for x and y
https://github.com/SciML/BoundaryValueDiffEq.jl/blob/fcb3f40e7cddf8aa1a22528f434ebe336c3ff554/src/collocation.jl
Actually easy to fix:
Proposed fix