We have a universal PL/SQL library attached to each form: UCS20.PLL. This library itself references WEBUTIL.PLL. Then some form modules use some other libraries like in the following example.
We've been aware of the fact, WEBUTIL.PLL should always be listed as the first one in the list or there will be errors like a form being terminated as soon as it starts. Now it happens sometimes that new libraries are introduced, but preceeding UCS20.pll library. Such a form will not run and ON-ERROR trigger will be raised:


If I implement the trigger, I get this info when debugging:


Now, I change the order of the libraries and suddenly everything works and the form is run successfuly:

Is this a bug or is there any specific reason behind it? At least errors should be more descriptive and make resolving such issues easily.
Oracle F&R v. 12.2.1.19, April 2025 quaterly patch applied on server side, Builder is standalone installation on Windows 10 Pro 21H2, Server is on Windows 10 Pro 22H2.