1-wire : 4.7k resistor not working / how to compute optimal resistor topology for star layout
From my memory of the Dallas guide, which should be similar, star layout should be avoided as the various reflections can cause interference. Without an oscilloscope it will be difficult to debug.

Assuming that you don't want to rewire, your most robust solution would be to put each cable on a separate pin of your micro and poll each individually.

You don't specify whether you are transmitting power on the data line or separately. The separate power line makes the resistor value less critical.

By the way, your 3.6k resistor isn't 'virtual'. It's real!