In my testing I registered two methods with the same name but different casing, e.g. "Method" and "method". This is not necessarily best practice, but at least it's technically ok because one is able to disambiguate this in the query/expression with quotes. For example, the expression e."Method"() matches and thus calls the first registered method.
When I forgot the quotes, NQuery correctly detected this as AmbiguousInvocation and failed. Unfortunately, the CompilationException's SourceRange property is equal to SourceRange.None instead of the expected column and line information.