Comparable l and n Issue

[ghost]

For a region of the complex frequency plane, the root finding algorithm cannot find the frequency corresponding to the specified l and n.
This region corresponds to 6 <= n, 3 <= l <= n, approximately, and is due to the presence of singularities in the Wronskian which drive the root finding algorithm away from it's (poor) initial guess and to the wrong root.

Possible fixes:
i) Improve initial guess in this region
ii) Within this range of l and n, cycle through l and n, generating lists which can be used to eliminate roots corresponding to indices other than the ones we're interested in.
iii) Find a way to specify, in general, the region that FindRoot should search, preventing FindRoot from being driven towards the incorrect root (linked to (i))