We're long time VME users, and are currently backing up a variety of VMware clusters and servers. Recently though, I've started to get errors for random VM's. This could be 2-3 VM's out of 20 that are part of a multi-VM backup, and not the same VM's every time. One night they will back up correctly, the next night they will fail. Others in the same set will backup ok. The specific error I'm getting is;

Failed: Cannot examine files of <VM name>: Cannot find <VM Name>-Restored.vmx (VMXLib.Logic.Browser.ESXiBrowserWithCompression: Cannot complete login due to an incorrect user name or password.)

If I validate the credentials for the vCenter appliance and cluster, they check out fine. The cluster and hosts are stable, and in this case, it's a vSphere 6.5 U3 cluster, so not the latest. We started getting these errors out of the blue in 7.1.1, and it hasn't made any difference upgrading to 7.1.3. I've no idea why it's started or how to fix it.