Sterling silver 18” necklace

Chain is in good condition and kept in a clean smoke free home. ** a few links approximate 5mm are tight** When feeling along the chain top side up it’s all smooth beautiful and shiny. When you flip it over it’s beautiful and shiny but you can feel a very small area approximate 5mm that’s stiff. It articulates fine and cannot be seen. Now if this is something that can be worked out like a kink-I don’t know enough about jewelry to mess with it. Most wouldn’t mention it because it does not affect the look or wear. - - I believe it’s vintage So still in good condition. 18” sterling silver chain has 3 areas marked 925, no other markings, brand unknown. 4mm X 1mm or less Weight 4.47 grams #jewelry #sterling-silver #925 #necklace