Two Settings toggles, both off by default, show what happened during a submission:

• Generate debug.log - writes the full trace to debug.log in the shared Yatate/Output folder on every submission, plus error.log with only the errors (empty when there were none). Lines are prefixed WARN: or ERROR: , so a tool can grep them.
• Show Debug Log in Preview - adds a Processing Log button to the Output Preview showing the same trace in the app. Its icon turns amber for a warning and red for an error, and the log opens by itself when there is an error.

The Processing Log is captured for every submission whatever the first setting says; that setting only controls whether it is also written to disk.

console.error(msg) in validate.js or process.js records an ERROR: line and stops the script, the same as an uncaught error.

Common causes

• A computed value doesn't reach a block. Put it on inputs (inputs.total = ...); a local var never reaches a block. Blocks see inputs as it was when their layout was placed.
• A block renders nothing. An image with no source, a scan code with no data, or a failed condition omits the block quietly. Check the Processing Log for a warning.
• The editor and the PDF differ. The Overlay Editor shows one layout file. Pages, and which layouts go on them, come from process.js, so only the preview shows the whole document.