It appears that the method of connecting all the sensors to the patch panel making a star topology could be the real issue. If I change to a single route I have one question? Do I need to join the end back to the start to make a loop or just have the furthest sensor and the end connection?
If you're doing it with networking cable, yes.
When I've done that I wire as follows:
At the panel:
pin 2 all sockets together in parallel, connected to +5V supply
1-wire data to pin 4 of first socket
1-wire ground to pin 5 of first socket
pin 6 of first socket to pin 4 of second socket
pin 3 of first socket to pin 5 of second socket
pin 6 of second socket to pin 4 of third socket
pin 3 of second socket to pin 5 of third socket
My sensor cables at the patch panel end are wired up with standard T-568B network cables, which means 2-orange, 3-green/w, 4-blue, 5-blue/w, 6-green.
My sensor cables at the sensor end are wired orange to sensor power (5V), blue and green both to sensor data pin, blue/w and green/w both to sensor ground pin.
This basically gives you a bus with the blue pair is taking signals from the patch panel to a sensor and the green pair is bringing it back to the patch panel. At the patch panel you either need shorting plugs which are just dummy cables with blue and green shorted together and blue/w and green/w shorted together, or you need to make sure you populate the sockets from the first upwards with no gaps.
There's something else you can try if you don't fancy re-wiring all your sensors - a trick for star topologies. Put a 150-ohm resistor at the base of each star arm on the data wire only. That is, on your setup, you'd disconnect your data wire from the back of each socket, and in its place punch in one leg of a 150 ohm resistor at each socket. Then you'd connect up all the other ends of the resistors with a wire that goes to the Pi. One and only one resistor should be in the signal path between the host adaptor (ie Pi) and each sensor, so if you had two sensors up a single wire, you'd still only have the single resistor at the panel. I don't know why it helps (my analogue electronics knowledge doesn't extend that far), but apparently it does.
This wiring scheme is compatible with a number of commercial systems - data on blue and ground on blue/w seems teh most common system, with power supply on orange. Some devices propose an auxillary 5V supply on teh green pair - by wiring using that pair as the 'data return' at least you don't introduce anything more than 5V onto teh data bus. Some devices propose teh brown pair as an auxillary 12V supply, so you don't want to use that pair.