Hi Daniel,
Please provide the following information for our analysis:
1.Are they 2010 workflows or 2013 Workflows?
2.Do you use built-in workflows or create them in SharePoint designer? If it is created in SharePoint designer, please provide a screenshot of how you design the workflow.
3.Use another account (site owner) to start the workflow manually to see the result.
4.Create a new list/library in the affected site collection and check if you can reproduce it.
5.Let us know if the issue occurs to all workflows (including in-built workflows) in
different site collections.
In addition, we need related trace logs and your tenant information to check it from backend. To protect the privacy, please access this URL to check details:
https://answers.microsoft.com/en-us/privatemessages/list
Thanks,
Sky