n4cl4n joined the community
I had the same problem, very reproducibly. Luckily, I found a workaround: Go to the document you want to copy a symbol from an duplicate it (in order to not mess up your old document). Select the duplicate an open the symbols palette. Open the menu with the three bars on top and select „separate symbols in selection“ (or similar, my language is not set to English). After that I could copy the element in selection and paste it to another document.