User with permission "Settings (eHoldings): Can assign/unassign a user from a KB" can't assign users to KB credentials

Overview: User with permission "Settings (eHoldings): Can assign/unassign a user from a KB" can't assign users to KB credentials
Steps to Reproduce:

1. Log into Snapshot FOLIO environment as User with at least the following permission:
   eHoldings: Can view providers, packages, titles detail records
   Settings (eHoldings): Can assign/unassign a user from a KB

2. Navigate to "Settings >> eHoldings >> Assigned Users"

3. Click on the "Assign users" button.

4. Find and select any user in the displayed pop-up modal.

Expected Results: The selected user assigned to KB credentials. User is displaying in the list at "Assigned Users" pane.
Actual Results: The error "Unable to complete this operation. Please try again." is displaying. "500" error is displaying at "DevTools>>Network".
Additional Information: See attached screencast.
This issue isn't reproducing with admin user permissions (admin_diku / admin).
Interested parties:  

Approach:

• Add "users.item.get" permission to POST "/eholdings/kb-credentials/<credentialsId>/users" endpoint modulePermissions

• Add "users.collection.get" and "usergroups.collection.get" permissions to GET "/eholdings/kb-credentials/<credentialsId>/users" enpoint modulePermissions

• Remove PUT "/eholdings/kb-credentials/<credentialsId>/users/<userId>" enpoint from module description