Unable to create an Activity within Profile
If a user is trying to create an Activity within Profile and is greeted with an An error occurred when saving the record [-1] error message, this would be advising the user that one of the related records that have been placed within this event has no relation to another record.
An example of this
If the user attempted to create a new Offer event for a candidate but in the Offer event, they placed insert a Contact who is at the Organisation but is not related to the Vacancy record, this would generate the error message.
To correct this, advise the user to make sure all records who are within the event are related to the Candidate/Contact/Organisation/Vacancy records.