The action after taking a screenshot freezes citrix session

We are using Greenshot in terminal sessions that are provided by Citrix XenApp/XenDesktop on a Windows Server 2016.

Sometimes it happens that Greenshot freeze the complete Citrix session. This happens when you have already chosen the scope of the screenshot and click on the button for the following action (save as, open in image editor, copy to clipbaord, print...). The window freezes and the whole desktop shows no more reaction. In those cases you then have to kill the client session and restart it.

Any idea what could be the problem here?