Land Rover Repair: Discovery 1 ABS fault, chassis number, stub axle

Question
I live in Hong Kong and drive a 1998 Discovery I with 3.9 EFI V8 engine.  The Engine number is 36D76610C.  The chassis number is SALLJGMM3WA798312.
In recent months, the ABS warning light keeep coming on.  I use the Hawkeye diagnostic tool and it returns the error "Left front sensor gap too wide".  I have tried pushing it back and replacing the sensor, and the fault remains.  Other fault codes suggesting "broken circuit', "intermittent disconnection during driving" also come up.
On some occasions, the warning light would not come on.  But the brakes will shake when the car is about to come to a standstill.  It seems ABS has been engaged even though it is not called for.
I suspect that the ABS ECU is at fault and would be most grateful for any advice you may have on solving this problem.  Thankyou.

Answer
The gap error can come from a weak sensor but it can also come from loose bearings in the hub (allowing the axle to wobble) or from corrosion or damage to the reluctor ring on the stub axle.  Check the bearings for play and also look closely at the reluctor ring which is visible through the hole if you remove the sensor.   And make sure the sensor is tightly seated by tapping with a rubber mallet.