Swap the bulb with another one and see what happens. Different lighting technologies need to be dimmed in different ways (and some can't be dimmed). Someone may have put in a replacement bulb with the wrong specs.
Thanks will try, all were put in same time as new extension. But worth a try
@Simpson started
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Swap the bulb with another one and see what happens. Different lighting technologies need to be dimmed in different ways (and some can't be dimmed). Someone may have put in a replacement bulb with the wrong specs.