Rust spot after first use / cleaning

I understand that these knives are not designed for dishwashers, but I have had a mixed set of very similar knives from two of the big name manufacturers that I have washed in the dishwasher for years with no problems. I always take care to remove solids from the knife promptly and give it a quick initial scrub before putting into dishwasher. I've had that prior set of ~10 knives for 8+ years and they are only now starting to show small rust spots. This knife unfortunately showed a rust spot after a single use/wash.

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