As the topic title indicates I have the following problem.

I stole "Stenvar`s Gold Ring" of Stenvar in Whindhelm
But when I deliver the item to Delvin, he instead removes my enchanted Gold Ring named "Resistance Ring" (enchanted with magic and fire resistance hence the name)

I have seen this on several other occasions as well, in any version of the game. Makes me beleive it might be quite rare.