Entries in the activity stream for records created before a clone appear to be created by the incorrect user in the target instance after cloning.
If you are experiencing this issue, all of the entries in the activity stream will appear to have been made by the same user. The records that are affected by this issue will have been created prior to the clone that excluded the audit data. Any updates to these records after the clone will appear correct in the activity stream because they are creating the audit data as the record is saved.
The instance was cloned with the "Exclude audit and log data" checkbox checked. This will cause the system to exclude the data for who created the entry.
Clone the instance again, but be sure to include the audit and log data.