An action set which is within a parrallel branch is set to run with highest privileges to allow the workflow tasks to override user permissions and write in a specific list. 

The tasks within the action set work fine for an administrator role however they fail for the rest of the users.

Solutions already tried:

• Removing the action set from a parrallel branch - still tasks fail
• Re-activating site feature 'Workflows can use app permissions'