Comment 3 for bug 1498620

This looks like a issue with the writable-paths in some way, both /etc/ppp and /etc/modprobe.d are at the wrong level. /writable/system-data/etc/modprobe.d/modprobe.d contains also a wrong level. Both of these files are marked as:
"""
/etc/modprobe.d/ auto persistent transition none
/etc/ppp/ auto persistent tran
"""
Note the trailing "/". I suspect this confuses the writable-path code in the initramfs.