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If you keep losing residual magnetism like that, it is due to a bad rotor. Something has happened to the physical properties of the steel to not allow it to hold residual magnetism.
Your only option is to live with it or replace the rotor.
Rewinding would do no good. It is not the windings that hold the magnetism - it is the steel itself.
If you have another rotor, you could swap it out.
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