Speedo is from Left Hand Rear Sensor on the L322.
Decent Land Rover specific diagnostics are needed i nthe first instance.
The ABS ECU is prone to failures, cheifly heat damage from sitting over the left hand exhaust manifold and also from moisture tracking along the loom into the connector - there was even a Tech Bulletin about this and the re-work is to replace the short harness that goes to the ABS ECU.....
I have indeed had ABS system issues, intermittement ABS faults that I just couldn't trace. I replaced the short harness no joy, I then replaced the ECU and that solved it. I then took the old ECU apart and found heat damage to a couple of the tiny internal wires, I did a write up and vid of the issue sometime a while back.
But we can surmise till the cows come home, first is getting on good diagnostics and see whats what.