Remove-PNPGroup results in "Object reference not set to an instance of an object"

[Tom-CK]

Running

Remove-PNPGroup -Identity [a 100% valid group name] -Force

results in an exception "Object reference not set to an instance of an object".

I validated the name of the group.
Running Get-PNPGroup with the same groupname is working well.

My environment:

• PNP.Powershell 1.5.0
• SharePoint Online Modern Teamsite

I use

Connect-PNPOnline -Url ... ClientId .... -ClientSecret ....

to connect. ClientId and Secret ist valid (working with other commands).
The app is registered with "scope="...../sitecollection" Right="FullControl".

When I connect using my account (-UseWebLogin) the command works well.