Personally I have never had a problem. Maybe i am lucky but mostly I just park it and leave it when shopping or sightseeing.
But, I do take sensible precautions about where you leave your bike and what you leave on it. For example if I left my bike overnight unlocked on the street in the centre of a major city with soft luggage I would be pleasantly surprised if it was all intact in the morning, in fact if the bike was still there. But in a pub or hotel car park in a village or small town I would be very surprised if anything was touched.
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