This could be due to the Replication Share having network communicating issues with some of the 6.4 KACE Agents which caused the Agents unable to copy and download the installer file.
On those 6.4 KACE Agent devices, go to C:\ProgramData\Dell\KACE\user\KAgent.log and examine further:
[2016-12-16.07:52:37][runkbot:DownloadDependency] Downloading dependency from alternate location [\\Repl_Share\KACE$\repl2\kbots\5\ampagent-7.0.763-x86.msi.beb733ff09f66b15f9c3c1f3f8ecc40f]
[2016-12-16.07:52:37][runkbot:KCopyFile] Error (win) copying files from '\\Repl_Share\KACE$\repl2\kbots\5\ampagent-7.0.763-x86.msi.beb733ff09f66b15f9c3c1f3f8ecc40f' to 'C:\ProgramData\Dell\KACE\kbots_cache\packages\kbots\5\ampagent-7.0.763-x86.msi' : (5) Access is denied.
[2016-12-16.07:52:37][runkbot:KCopyFile] Error (win) copying files from '\\Repl_Share\KACE$\repl2\kbots\5\ampagent-7.0.763-x86.msi.beb733ff09f66b15f9c3c1f3f8ecc40f' to 'C:\ProgramData\Dell\KACE\kbots_cache\packages\kbots\5\ampagent-7.0.763-x86.msi' : (5) Access is denied.
[2016-12-16.07:52:37][runkbot:DownloadDependency] Downloading dependency from alternate location [\\Repl_Share\KACE$\repl2\kbots\5\ampagent-7.0.763-x86.msi.beb733ff09f66b15f9c3c1f3f8ecc40f] - Failed
Try to check on the Replication Share or Disable it and let all the version 6.4 KACE Agents download the KACE Agent installer file "ampagent-7.0.763-x86.msi" directly from the K1000 Appliance.
Other possibilities on the Replication Share that causes the Agents unable to download or copy: