ABS Wheel Speed Sensor Gap

I have had a rt ft wheel speed sensor not reading correctly/intermittent. The sensor ohms out at 1.09 (which is fine according to the Bentley) and the connector is fine and not corroded. I checked with VAG-COM while driving and the sensor is definetly not reading like the other 3. I cleaned it, checked for warpage and trueness of the ring. Still not reading correctly. Maximum gap of the sensor & ring is not listed in the Bentley CD.
I have not checked the wires from the connector to the brake Elec control unit. VAG-COM GP 3, Blk 2 shows 2 on all for wheels, which I assume means the voltage is correct.??

Through experience, does anyone know what the maximum gap is between the sensor and the ring before you get intermittent signals? or any other ideas?

Thanks

According to my 98 NB CD the gap is from the rotor to speed sensor is 3 mm (0.0188 in). Hope that helps.