We’ve had exactly the same on Choupette. Particularly when turning them on to check them with the shore power attached. I have discussed with Hella Marine Engineering in Austria and they advise that the commonest cause of premature failure is high voltage spikes weakening the filiament.

    Our 25A shore power charger does seem to charge at high voltage rates but the Bavaria distributor here in France advised that this was normal.

    I am now replacing ny bulbs with LED replacements each time they blow as LEDs work in a wider voltage range.