Eli Zaretskii <eliz@gnu.org> writes:

> Can you attach a debugger to the wget process that's stuck, and see
> where it is stuck?  You will probably need to rebuild wget with debug
> info, or install one from your package repository (if they offer
> such).  This could give us hints for where to look further.

I did the following:

0. Build wget 1.19.5 from Debian's repositories:
   apt-get build-dep wget
   apt-get source wget
   configure CC='ccache gcc' CFLAGS='-O0 -g3 -ggdb -gdwarf-4 -pipe'
             --config-cache --enable-assert --with-gnu-ld
   make
1. Substitute resulting wget file name in original test.el program
2. emacs26 -Q -l test.el -f test-threads
3. gdb -p <pid of stuck wget>
4. set logging on
5. bt

I attach the resulting gdb.txt log file.

Thanks,

-- 
Basil