I have recently added two fields in calendar.event

room_id = fields.Many2one('meeting.room',string='Meeting Room',help="Location of Event",ondelete='cascade')

calendar_event_type = fields.Char(string='Event Type')
the purpose of these fields is to separate the meeting event in the calendar. I also have an onchage function to fill up calendar_event_type data when room_id is selected.

@api.onchange('room_id')    
defonchange_room_id(self):
        ifself.room_id:
            self.calendar_event_type ='event_type_meeting'
        else:
            self.calendar_event_type =False

but, when I try to create an event it gives the bellow error.

User Error: Failed to render inline_template template : Record does not exist or has been deleted. (Record: calendar.event(406,), User: 2))

It doesn't happen every time, it happens randomly.