On our partner community the users are not able to see the related to and assigned to fields.
Following below articles I changed org-wide sharing to private for all objects that could be linked to a task to private or disabled "track activities" on the object.
This did not change anything. Fields are still not visible.
FYI: I also checked FLS and the report type: fields are visible AND added to the layout.
Any of you have something I could try?