Buttons for looking left / right change to brake bias adjust

F1 24 on XBOX Series S

Thrustmaster T128 wheel and pedals, correctly setup with look left and look right bound to the LSB and RSB buttons, no buttons bound to brake bias adjust.

Either straight away, or after a short delay, the LSB and RSB buttons adjust my brake bias instead of looking right and left!!

The XBOX doesn't support anything other than standard widescreen, so from the cockpit view I can't see either of my mirrors without looking left and right.

?