I upgraded to 2.9.3 from 2.8.2 and it wiped out the credentials I had saved in the Variables. I imported them back in from the BuiltInLocalVault, but it only keeps the most recent creds added as a PSCred, the ones added before it turn into strings.
This is fixed in 2.10. The issue is that -Value '' is being added to the variable.ps1 credentials. You can work around it by removing the -Value '' from that PS1 file.
This is fixed in 2.10. The problem is when multiple jobs run at the same time. You can work around 2.9.3 by setting a random delay on the schedule but in 2.10 we synchronize access to the secret management and rolled back some changes we made that were not thread safe. We are using the standard secret management module again and not the patched one we had included previously.