Comment 18 for bug 1751813

Can you extract and attach the full installer log?
the /var/log/syslog from the running d-i, after doing all possible steps to get it working again
(e.g. the mentioned going back & rescanning disks).

For the installer, kernel modules are split into .udeb packages, and it might be that some of the needed kernel modules, are loaded after disk scanning was performed, hence rescanning picks up new things as new/more kernel drivers are loaded at that point.

Output of lsmod would be useful as well, to correlate and check which udebs are downloaded when; and which drivers are modprobed when.

E.g. it is possible that scsi-modules udeb is lacking the necessary modules in v4.15 packaging splits.