Follow up:
If I try to open one of these files, nothing really happens. I just get a black screen with a little "spinner" that keeps on spinning.
If I "select" one of these files, there is no option to "remove download", only to "remove from library".
The files also don't seem to be independent of each other. Are they all pointing to the same thing? I "removed" three of the four and then tried to open the remaining file and got a message that I would need to download it again. But of course there was no "not-downloaded" version anywhere, like in the "All" section, that could be downloaded!
While all four were still present in downloads I used a file manager to check in the Kindle directory and in the Amazon.kindle directory in Android/data. There were no 2.5gb files to be found anywhere. The " files" directory of the Kindle directory in Android/Data was only 3.6gb, which includes several audiobooks included with some ebooks. (I have a huge internal storage — 512gb — so I don't worry about storage space) So the 10gb supposedly used by these "no title" downloads doesn't exist anywhere I can see.
More than a curiosity, I get concerned that these are virus files inserted by some third party gremlin. (I use Bitddfender Mobile Security, which has never flagged anything.)
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