Thanks for sending the script. I tried to run it but it errored out, but it got me thinking and I decided to troubleshoot my VMDIR issue. I logged directly into the vCenter and ran these commands:

cd /usr/lib/vmware-vmdir/bin
./vdcrepadmin -f showservers -h localhost -u administrator
./vdcrepadmin -f showpartners -h localhost -u administrator

I found a legacy 7.0.3 vCenter which I had decommissioned long ago, but had not removed it properly. I tried to use Using the cmsso command to unregister vCenter with External PSC or vCenter with Embedded PSC from Si... to remove it, but that also errored out.

I was about to throw in the towel, but instead I pulled the old vCenter out of mothballs and brought it back online. Sure enough, that fixed the VMDIR error when upgrading the second 8.0 vCenter and the upgrade completed successfully.

I'll attempt to decommission and unlink this old vCenter properly next.

Thanks for the help!