It sounds like you did a thorough job on the starter but something caught my eye. The lower end plate in the photo shows a shiny ring on it. This could be from the thrust washer (#26) or from the commutator rubbing on it. I don’t see the separate thrust washer in your parts layout so it might be missing. I know it’s a PITA but you might want to go back in and measure the shiny ring against the end of the commutator or pull the armature out slightly with the end plate and brushes attached and visually make sure the commutator isn’t rubbing on the end plate. The thrust washer supports the weight of the armature and starter drive and does wear out, especially if water has made its way in.
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