Conversion Job Stuck at 47% (ePUB file)

I’m hoping someone can explain to me what I’m doing wrong here. If more information than provided below is needed, please let me know.

The problem I am having is that calibre is not converting my ePUB file. It’s a fixed layout ePUB file. I am using calibre to insert the cover (by using the “Change cover image:” box), and I am converting the original ePUB file to another ePUB file. I was able to recreate this with an identical ePUB (reflowable) file.

When I try to instead convert the ePUB (fixed layout) file to a mobi file, the same problem occurs, though the problem did not occur with the ePUB (reflowable) file.

There are no error messages.

The file size is 0.9 MB.

The last few lines of the conversion log are…:
The book already has a TOC, and I have no idea if “Source base font size is 158.40000pt” (a huge font size if I understand correctly) is a part of the problem?

Does calibre not convert fixed layout ePUB files?

To my knowledge, I did not change any of the default conversion options.