Keeping CDROMs plugged into Virtual Machines can inhibit DRS/vMotion from working well for these Virtual Machines, as such it is best practice to remove CDROMs when not needed, so follow the commands to identify them.
List all Virtual Machine with CDROM connect:
Get-VM | Get-CDDrive | Where {$_.extensiondata.connectable.connected -eq $true} | Select Parent
Disconnect all CDROM from all Virtual Machine
Get-VM | Get-CDDrive | Where {$_.extensiondata.connectable.connected -eq $true} | Set-CDDrive -NoMedia -confirm:$false