There’s kind of a cascade of serialized values here to beware of, each subsequent one having a chance to overwrite the previous one, if it exists.
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the value defined in code
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the value overridden in void Reset() (if present)
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the value saved in the prefab
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the value saved in the prefab override
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the value saved in the scene.
When in doubt, wipe these things out and create them afresh.
Here’s more insight into the problem:
Field initializers versus using Reset() function and Unity serialization: