Using 2 Tank Circuits to Determine the Position/Direction of a Wire
You have a flaw in your coil design. If the wire passes between the two receive coils at dead centre (irrespective of angle) you receive the same voltage for each coil: -



In any of the trajectories above you will get a reading of "middle".

You can partially fix this with fore and aft coils added to your design and processed seperately. I say "partially" but there will still be a false neutral position at 90 degrees.