Debian (network install) fails on "Installation step failed"
Looking into the logfile I read that the issue was with pkgsel. Searching the log I noticed a "FATAL -> Failed to fork."
Then I remembered that I was doing this on a virtual machine and looked at the settings. The memory was set to to 256MB. Increasing the RAM to 384 MB solved this issue. Wanted to share this in case you are also confronted with this memory usage situation.