I try now to Change the "Database Mappings" (in the Central Administration).

Actually it set on...   Any Available Workflow Database Content

to explicitely the one Content DB.

CentralAdmin: Monitoring - Review Job Definitions:

1. Stopped NINTEX Scheduler Job

2. Stopped Workflow Job

Then Central Administration - NINTEX - Workflow Database Setup --> Manage Database Mappings:

Change from... Any Available Workflow Database Content

to (new)....        NAME (of the Content database)....

Reset the IIS

The activate the two Job Definitions again.

Will test and post the result here....

No effect yet.

Further Information will follow a.s.a.p.

I found a message that the first wf in this process was chancelled by the "systemaccount".

??

A lot of times this error pops up when an action has timed out.   Have you opened the workflow in the designer to check and see if any configuration errors exist?  Sometimes they aren't noticeable until viewed inside the designer.   When moving from environments, references to "resources" such as lists can easily become broken.   There can also be issue with URLs no longer accessible from the new env.

Thanks

‌ did you resolve this in the end?  

Hi Cassy

It's been a Long time ago since this Problem occured. I think it's solved....almost now it works.