If you are upgrading to a version passed 10.1.15.2 you should not be affected by this issue.
Otherwise, when upgrading from Deadline versions less than 10.1.10.6 to versions from 10.1.10.6 to 10.1.15.2 you'll need to upgrade to 10.1.10.6 first and then upgrade to the version past it. This is because of a known bug in the upgrade process.
You'll see an error like below:
In the Installation Logs you'll see something like below (installation logs sit here):
Script stderr: Please Enter Certificate Password: Executing C:\Users\XXXX\Local\Temp\2/repoinstalltemp/deadlinecommand.exe RunCommandForRepository Direct "path_to\Deadline\Repository;path_toDeadline\Repository\Deadline10Client.pfx" IsSecretsManagementEnabled Script exit code: 1 Script output: Error encountered when loading the configured Client Certificate (path_to\Deadline\Repository\Deadline10Client.pfx). It is likely either an invalid x.509 certificate, or the wrong passphrase was provided. Full Error: The specified network password is not correct. Script stderr: Program ended with an error exit code An error occurred while trying to update database settings in the repository.
During the upgrade a flag "IsSecretsManagmentEnabled" is passed to deadlinecommand, Deadline version 10.1.10.6 was the first version to introduce Secrets Management functionality so it does not pass this flag but adds the functionality in the database. Now if you upgrade from 10.1.10.6, to any version up to 10.1.15.2 the installer will pass this flag and the database already has this value stored so it will not break on running deadlinecommand.
As of today we've pulled the old Deadline installers from out downloads website, so you need to cut us a ticket to get the installers.
Another workaround that has been reported, but has not tested, by one of the customers who ran into this issue. You can try doing an unattended mode installation, follow here to learn how: https://docs.thinkboxsoftware.com/products/deadline/10.1/1_User%20Manual/manual/install-db-repo.html#command-line-or-silent-installation