Go to the SharePoint multiline column setting, and change the return type to plain text instead of reach text. Then try again.
And also you could use string builder action in the SharePoint designer workflow to make good looking.
Sample Example on how description field was customized using the string builder here :
Nicely formatted Workflow Task ...
It would not work. The workflow would pause until the latest day and then send three emails together at that day.
Workaround, you could create three workflows instead. Then use the IM Policy to trigeer the three worflows.
It's by default that SharePoint 2013 workflow is in only sending to users known by the tenant.
As a workaround, you could use SharePoint 2010 workflow platform impersonation step.
Here is a similar post for your reference: How do you send emails to external email address in sharepoint online workflows
The Access Denied error is possibly triggered because the workflow itself doesn’t have permission to edit the list item.
Please check if you have Workflows can use app permissions feature activated via Site Settings > Site Features.
You can also try writing the workflow actions in App Step in SharePoint Designer 2013 to grant elevated permissions to the ...
Try following approach to replace item permissions:
Set a STRING variable to the multiple selection people picker field, returning the field as a STRING.
In an Impersonation Step, add the action to Add/replace item permissions and use the string variable you just created in above step.