Get-PnPSiteTemplate -Out ---- Object reference not set to an instance of an object

We are using PSVersion 7.3.4. The below code works with PnP 1.11.0, but not with PnP 2.2.1. This is the only difference. The issue occurs for a more complex site Template; with a fast empty Template it works with any PnP version. Please fix asap, this prevents us from automatical SiteProvisioning that used to work earlier with an old version!!!

$url = "https://mycompany.sharepoint.com/sites/testsite"
$templateUrl = "https://mycompany.sharepoint.com/sites/testsite/template"
$templatePath = "D:\temp\template\template.xml"
$clientid = "777777x7-x7x7-77xx-x777-77xxx77777x7"
$clientSecret = "x7x7xxx.77xxxxxx.xxxxx.x77x~xxx"
$con = Connect-PnPOnline -url $templateUrl -ClientId $clientid -ClientSecret $clientSecret -ReturnConnection
Get-PnPSiteTemplate -Connection $con -Out $templatePath -PersistMultiLanguageResources -Force
Get-PnPException

Message : Object reference not set to an instance of an object.
Stacktrace : at PnP.PowerShell.Commands.Base.PnPConnectedCmdlet.ProcessRecord() in
c:\build\src\Commands\Base\PnPConnectedCmdlet.cs:line 98
at PnP.PowerShell.Commands.PnPSharePointCmdlet.ProcessRecord() in
c:\build\src\Commands\Base\PnPSharePointCmdlet.cs:line 120
at System.Management.Automation.CommandProcessor.ProcessRecord()
ScriptLineNumber : 1

Start by reproducing the failure with Get-PnPSiteTemplate using the complex template and compare PnP 1.11.0 with 2.2.1. Trace the error through PnPConnectedCmdlet.ProcessRecord at c:\build\src\Commands\Base\PnPConnectedCmdlet.cs:98 and PnPSharePointCmdlet.ProcessRecord at line 120. Done means the complex template exports successfully without the null-reference exception.