Going Crazy, Need help with Powershell script

Here's the relevant section.  The problem I'm having is the calculated property for Manager Name and Manager Email is inconsistent.

For some users the below is returning empty values.  Check the #comment section, I've tried that way to.

I don't get what's going on, if I query those individual users (Get-Mailbox user then pipe the rest) it will come back with the calculated property just fine. 

If I run this section and watch the output, it looks like its walking the domain each time for the calculated value which is odd since the $_.manager is a DN value (assuming it isn't null) so the value should also be returned immediately.

FYI, This is Exchange Cmd-lets opened by Remote Powershell

Get-Mailbox -OrganizationalUnit someOU -ResultSize Unlimited | Get-User | Select @{N="Email Address";E={$_.WindowsEmailAddress}},
     @{N="First Name";E={$_.FirstName}},
     @{N="Last Name";E={$_.LastName}},
     @{N="Department";E={$_.Department}},
     @{N="Job Title";E={$_.Title}},
     @{N="Manager Name";E={Get-User $_.Manager | Select -ExpandProperty DisplayName}},
     @{N="Manager Email";E={Get-User $_.Manager | Select -ExpandProperty WindowsEmailAddress}} | Export-Csv -notype $path$file
     #@{N="Manager Name";E={$mgr = Get-User $_.Manager;$mgr.DisplayName}},
     #@{N="Manager Email";E={$mgr = Get-User $_.Manager;$mgr.WindowsEmailAddress}} | Export-Csv -notype $path$file