My Fiat Panda 1.2 dash cluster has been behaving rather strange recently. It relates to the 'left' directional indicator lamp on the cluster, as it fails to illuminate after 1 hour or so of driving.
When the vehicle is cold, it works perfectly, indicates correctly, but after 1 hour, the bulb just doesn't illuminate, and refuses to until the vehicle is stopped, left for around 1 hour or so and restarted. A quick restart doesn't reset it.

The exterior bulbs illuminate, regardless whether the cluster indicator bulb is working or not.

I have disconnected my battery for a few hours hoping to reset it, but to no avail. Fiat wants £571 for a new cluster and used clusters could be faulty, or have mileage higher than mine (which means I cannot re-wind the mileage on the new cluster, I've been told).

What are the legalities surrounding this? If the car was in for an MOT and the internal indicator bulb failed to illuminate, would it be classed as a fail? It's the only fault relating to the cluster, everything else works as it should.