So circling back on this from the thread I previousl;y started that Roger shut down - not sure why he did that. Roger ?
Here is what I figured out.
It is not a "lost" neutral, as in, the result of a broken wire, etc.
The circuit includes a 4-way switch in the middle of two 3-ways BUT, 12/2 was used for the travelers, not the standard 12/3, so no neutral passing through the middle box that contains the 4-way, hence the need for the "mystrey neutral" to complete the circuit.
Here is what I figured out.
It is not a "lost" neutral, as in, the result of a broken wire, etc.
The circuit includes a 4-way switch in the middle of two 3-ways BUT, 12/2 was used for the travelers, not the standard 12/3, so no neutral passing through the middle box that contains the 4-way, hence the need for the "mystrey neutral" to complete the circuit.