Copy references between documents

I have a problem copying text including references between the documents. I have never needed that until now so don't know if this is a new problem or not - have been using Zotero happily for 5 years now

I am running libreoffice fresh 6.1.2-1 with Zotero 5.0.56 libreoffice connector add in on linux

To reproduce the problem
1) make a new document, save it as xy.docx
2) insert reference, chose citation style and choose to use bookmarks to store references
3) copy/paste text including reference field code from an old document into the new one. BTW the old document has the same references settings/style as the new one
4) insert bibiolography in the new document - the reference copied from the old document is not recognised and doesn't have field code/can't be edited

The same problem occurs if the step 2 is replaced by just setting the zotero bibiolography preferences in the new document.

What is the problem here? I though this was a reliably working feature by now.