Removing Old ActiveSync Devices Exchange 2010 Powershell

Any suggestions on what I'm doing wrong with this script?

$Mailboxes = $null
$Devices = $null

$Mailboxes = Get-CASMailbox -Filter {HasActivesyncDevicePartnership -eq $true} -resultsize Unlimited

$Devices = $Mailboxes | %{Get-ActiveSyncDeviceStatistics -Mailbox $_.Identity} | ?{($_.LastSuccessSync -ne $null) -and ($_.LastSuccessSync -le (Get-Date).AddDays(-14))}

$Devices | %{Remove-ActiveSyncDevice -identity $_.guid}

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Error Message: "Cannot process argument transformation on parameter 'Identity'. Cannot convert the "8712635a-1ec2-4860-a654-121167c888d9" value of type "System.Guid" to type "Microsoft.Exchange.Configuration.Tasks.ActiveSyncDeviceIdParameter".
    + CategoryInfo          : InvalidData: (:) [Remove-ActiveSyncDevice], ParameterBindin...mationException
    + FullyQualifiedErrorId : ParameterArgumentTransformationError,Remove-ActiveSyncDevice"

However, when I use the GUID property tag in an individual "remove-activesyncdevice" cmdlet...it works.

Also, if I use the $_.Identity variable in place of the $_.GUID variable it works for some users but has trouble with others. Saying it cannot find the recipient