[FIX] there was search on all records instead of current one

booking_calendar/models.py

@@ -666,6 +666,6 @@ class SaleOrder(models.Model):
     @api.multi
     @api.constrains('state')
     def _check_state(self):
-        if self.search_count([('state', 'not in', ['draft'])]) and \
+        if self.state not in ['draft'] and \
            self.env['sale.order.line'].search_count([('order_id', '=', self.id), ('overlap', '=', 'True')]):
             raise ValidationError(_('There are lines with overlap in this order. Please move overlapping lines to another time or resource'))