以下のごく普通？のjsonがConvertFrom-Jsonだと意味不明なエラーで通らなかった
'{"":"あーあ" }' | ConvertFrom-Json
エラー出力
ConvertFrom-Json : Cannot process argument because the value of argument "name" is not valid. Change the value of the "name" argument and run the operation again.
At line:1 char:17
+ '{"":"あーあ" }' | ConvertFrom-Json
+ ~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidArgument: (:) [ConvertFrom-Json], PSArgumentException
+ FullyQualifiedErrorId : Argument,Microsoft.PowerShell.Commands.ConvertFromJsonCommand