found an issue in exchange Nintex Workflow files between Nintex Version 184.108.40.206 and 220.127.116.11:
On Nintex 18.104.22.168:
In a task (Request Data in my Example) I leave the Item permissions to Unchanged:
If I export this workflow and re-import on a machine with Version 22.214.171.124 installed I get this:
If you start such a workflow you will get the message that start is failed and it retries to start the WF infinitely and produces the task several times...
Here is the difference found in the nwf files:
My conclusion: Never run different versions of Nintex on development and prod environments :-)
Hope this helps someone to avoid time consuming error analysis.