org-export-async-debug

org-export-async-debug is a variable defined in `ox.el'.
Its value is

nil

Documentation:
Non-nil means asynchronous export process should leave data behind.

This data is found in the appropriate "*Org Export Process*"
buffer, and in files prefixed with "org-export-process" and
located in `temporary-file-directory'.

When non-nil, it will also set `debug-on-error' to a non-nil
value in the external process.