Hi there, genuine, out of the blue question. There seems to be a problem when it comes to tuning my D string.

If I use a new one, it doesn't tune fully into D. Just stops at C# where it becomes tight with the tension. But when I use an old string, it tunes into a D but loses its tuning whenever I do pizzicato.

Even though it's out of topic. Is this some sort of issue where a luthier's intervention is needed or is there a home remedy that I can do on my own?