Lightroom Downloader finds files that were deleted but cannot download them because they don't exist

When I use the Lightroom Downloader, the report lists many files with the message "Requested download not found" (translated from the German version). Besides these files are stated as "type: video", which is not correct. When I search for these files, I find that they are photos that have been deleted. I still find them on my memory card, but not in Lightroom, and I remember that I deleted them deliberately. So there must be records in the database without content, and they become more and more over time. How can I delete these records? And how does it happen? I assume that it happens when I quit Lightroom while the upload hasn't finished, which can occur due to slow internet speed when I can't wait for the upload to complete. Or when I delete photos while others are still uploading, which is a normal behavior.

Lightroom 6.4 on macOS 11.7.8