Build says Latex could not compile file but it doesn't appear to be true

[raffaem]

Running

bookdown::render_book("index.Rmd", "bookdown::pdf_book", output_dir="./PDF")

ends with:

Error: LaTeX failed to compile book.tex. See https://yihui.org/tinytex/r/#debugging for debugging tips. See book.log for more info.

The last lines of book.log are as follows:

Here is how much of TeX's memory you used:
 21646 strings out of 481677
 421366 string characters out of 5932691
 820033 words of memory out of 5000000
 38244 multiletter control sequences out of 15000+600000
 543574 words of font info for 106 fonts, out of 8000000 for 9000
 14 hyphenation exceptions out of 8191
 60i,8n,118p,1460b,576s stack positions out of 5000i,500n,10000p,200000b,80000s

Output written on book.pdf (269 pages).

And the book.pdf file is present.

So it appears that the first error message is wrong?