Copy over AppData from one SDL Web Content Manager item to the other. I used this script to repair a Media Manager ECL stub schema after content porting it. During Content Porting somehow the AppData was lost and with this script I restored it from another working ECL stub schema.
$sourceEclStubSchemaId = 'tcm:25-557-8'
$targetEclStubSchemaId = 'tcm:25-368-8'
$ErrorActionPreference = "Stop"
# Using Tridion Powershell Modules from https://github.com/pkjaer/tridion-powershell-modules
Import-Module Tridion-CoreService
$core = Get-TridionCoreServiceClient
$appData = $core.ReadAllApplicationData($sourceEclStubSchemaId)
## Danger Zone - uncomment the following lines if you know what you are doing
#$core.SaveApplicationData($targetEclStubSchemaId, $appData)
#Write-Output "Copied AppData from $sourceEclStubSchemaId to $targetEclStubSchemaId"
Write-Output $appData