We're having a problem where we are continuously having to manually recalculate sharing rules in an org.
Account OWD is set to Private.
Sharing Rule 1: Account lookup field is populated by a certain record grants read/write access to Public Group 1.
Sharing Rule 2: Account Owner is in All Internal Users grants read/write access to Public Group 2.
Therefore, everyone in Public Group 2 should have Read/Write access to ALL Accounts, Contacts, Opportunities, Cases and all related Activities (because all Account Owners are in All Internal Users).
Once every few weeks, a user puts in a ticket stating they can't see Tasks (related to Accounts) they don't own or they can't transfer a Task (related to an Account) to another user.
Recalculating the Account Sharing Rules always fixes this issue, but despite having a ticket open with Salesforce for almost two months now...we can't figure out why the problem is happening in the first place.
Any ideas what could be the root cause of this issue?