JOC is not available for a backup JobScheduler while it is waiting for activation

You cannot open JOC for the backup JobScheduler in a JobScheduler Backup Cluster until it get active. In the scheduler.log you get the error:

[ERROR SCHEDULER-212  Missing entry [spooler] html_dir= in file factory.ini]

The entry exists and has the right value = ./operations_gui

It seems that the factory.ini doesn't read while the backup JobScheduler is still waiting for activation.
Further JOC cannot be open via Jetty too.