Avoid defining public or serialized properties in general, as pointed out above. Here’s why:
Serialized properties in Unity are initialized as a cascade of possible values, each subsequent value (if present) overwriting the previous value:
what the class constructor makes (either default(T) or else field initializers)
what is saved with the prefab
what is saved with the prefab override(s)/variant(s)
what is saved in the scene and not applied to the prefab
what is changed in Awake(), Start(), or even later etc.
Make sure you only initialize things at ONE of the above levels, or if necessary, at levels that you specifically understand in your use case. Otherwise errors will seem very mysterious.