Hello Alain, just saw your report and though it sounds similar to another one [1]. Do you have linux-image in version 4.9.130-2 installed? Were older kernels working like expected? If possible you might want also check if reverting back to 4.9.110-3+deb9u6 gives you a not hanging system on eject.
Kind regards, Bernhard [1] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=914696
