We have a user (User A) in the main business unit that creates and owns call records that are attached to accounts/contacts/leads. These account, contact, and lead records are owned by users in a lower business unit. In the lower business unit we have 2 types of users, salespersons and sales managers. Salespersons can only view their own records while sales managers can view any record in their business unit. The issue occurs when User A creates a call record on a salesperson's account record. The salesperson can see User A's call record in the timeline just fine but the sales manager can not. The sales manager can see User A's call record only if it is regarding an account that the sales manager owns. This issue is replicated if any user in the main business unit tries to create a call record on a lower BU account. Is there a possible fix to this without changing the read privledges for the sales manager and without changing any of the record ownerships?

Attempts at a Solution:

Used a test Security Role to give different read privlidges, the only one that allowed the user to see the activities was Organization Read privledges on the Activity Entity.

Owner teams would not work as we don't want to change the ownership of any of the records if possible.

Access teams would not work as this needs to be available for all account/contact/leads/activity records at all times.

Thank you for your time.