`Add-Member` errors when calling `Get-Turtle`

[ninmonkey]

To reproduce

> Import-module ./Turtle.psd1 -Force -Verbose
> $error.clear()
> $t = Get-Turtle

# Error: The SecondValue parameter is not necessary for a member of type "NoteProperty", and 
#    should not be specified. Do not specify the SecondValue parameter when you add members of this type

> $t.Position

# Error: The SecondValue parameter is not necessary for a member of type "NoteProperty", and 
#    should not be specified. Do not specify the SecondValue parameter when you add members of this type

> $error.count # 3

> $null -eq (Get-Turtle).Position
# true