There can be times when you might have to face an error in the compose feature of Yahoo and that might cause you trouble. In such an event, the best way to solve the problem is to use the tricks that are available in the tech help websites or you can call the customer care to speak to a Yahoo representative.
https://www.contact-mail-support.com/yahoo-customer-support/
https://www.contact-mail-support.com/yahoo-customer-support/