More advice needed, ABS working but warning light is on

The ABS warning light has appeared on my 2005 Defender XS
Also the traction control light (next to the ABS light) disappears normally on start up but re appears randomly.

l just collected it having had new rear discs and pads fitted, but looking underneath both the sensors appear to be in place on the rear hubs.

l tested the ABS and it does appear to work, the pedal goes lower when it kicks in but it’s definitely stopping the wheels from locking up.

Is there anything l can check? Its my missus’s Landy and she won’t drive it with the warning lights on however much l reassure her.

l can’t take it back until next week. Once the warning light comes on does it stay on even if the fault clears?

On the rrc, any movement in the wheel bearing fires up the warning light. Tighten bearing and it goes away. Think yours will be the new discs fitted and best to take it back and give them a chance to fix it.

The ABS lights were reset by my local LR specialist and have stayed off.
The ABS was made to work a few times (fairly easy as the roads were wet), and is working.
The garage said that it was coming up as a shuttle valve, they said if you drive a Defender carefully the ABS never kicks in and the valve can stick, they advised to occasionally get the ABS to operate if possible.
It didn’t cost me anything, which was good news!