General purpose document repositories like Zenodo obviously contain a range of different document types, unlike other common sources that tend to have just one or two. I am not sure what clues Zotero can look for from Zenodo to categorize that wide range of documents, but some are just going to un-categorizable based on the the information they provide. The same thing happens on Researchgate. Zotero often ends up having to give a Book item type to conference papers for example.

It's always best to check the metadata for *all* items as they come into Zotero, and edit anything that's not quite right. Changing journal article titles to sentence case is probably the change that I have to make most often - journals sometimes provide them in title case.

In this case with Zenodo, just change the item type to the one that is most correct. As long as you know what it is, and it gets cited in the right way in a bibliography, that's all that really matters.

Is somebody working on fixing the Zenodo translator? I didn't see any open issue or pull request.

I have started work on an updated translator. It isn't working yet, but there's been some progress... I'll submit a pull request if I manage to pass the tests.

Pull request submitted: https://github.com/zotero/translators/pull/3202