One of the first things I noticed when making an APEX application, there was a lack of error handling. In particular, the error handling raised from an database procedure. For clarity, here a part of a screen as you will see after a unique constraint violation, the ORA-0001 error. I think the most horrible part is that this error is displayed on a new page!
I solved this problem for my situation, perhaps it can help you too.
Copy and paste this URL into your WordPress site to embed
Copy and paste this code into your site to embed