This issue only arises after the addition of FFI::shutdown() in index.php however if you don't call the shutdown function the memory used by the container accumulates - usually until it is killed.
docker build -t libvips-segfault-repro .
docker run -it --rm -p 8000:80 libvips-segfault-repro
Run apachebench to make some volume of requests or just keep hitting refresh in a browser
ab -n 100 -c 5 http://localhost:8000/
Watch the output from the container and observe the SEGFAULTS
If you want to run the container with the local volume mounted run
composer install and mount the current working dir to /var/www
docker run -it --rm -v $PWD:/var/www -p 8000:80 libvips-segfault-repro