Enonic XP 6.3.0 has a problem with the export/dump of manually sorted content.
If you are using 6.3.0, you should first upgrade to 6.3.1 (No need to dump & load between 6.3.0 and 6.3.1).
Unexpected error: Failed to get children of path ./dump_23.02/cms-repo/draft/content/[SOME_PATH]]
The upgraded folder is one third in size of the original. Upgraded folder also gets named [ORIGINAL_NAME]_upgraded_6.0.0 even though the original dump is from 6.3.1.
You don’t need to do the dump/upgrade, only use the export feature of the 6.3.1 toolbox (important, 6.3.0 had major errors in export format). Then go to 6.4 and import it (6.4.0 had some minor issues, a 6.4.1 will soon be released, no need to upgrade between these two though).
Any reason why you describe dump/load as preferred upgrade steps in your doc ?
Is there a way to make the export command export all repos, or do I have to export each one (I only know of cms-repo and system-repo, are there more ?) separately ?
First switch your installation from 6.3.0 to 6.3.1
Dump the data
Go to your clean 6.4.0 installation and upgrade the dump using this 6.4.0 installation (You will see that the folder will have a name [ORIGINAL_NAME]_upgraded_6.4.0 and not [ORIGINAL_NAME]_upgraded_6.0.0)
On your 6.4.0 installation, load the upgraded dump
But I am interested by your error “Failed to get children of path ./dump_23.02/cms-repo/draft/content/[SOME_PATH]]”. What it means is that it fails to read the children files of the mentioned directory (Unfortunately it is not verbose enough, we do not see there reason of the failure). Could be some missing access permissions for example