Get more details about log messages I'm getting a lot of "Missing text format: 1." errors in my log. It seems to point to a bug where text formats used to get referenced by number in D6 (['format'] = '1') but now are referenced by a name in D7 (['format'] = 'plain_text').

How would I find where does bugs are?

Or a more general question: how can I get more details about error messages in the Drupal log?
Guess log means watchdog here. Generally, you only have what the developer passed to the watchdog.

You can try to parse the code for (a part) of the error message. There's a good chance that this points you to the code sending the watchdog, which in turn gives you more information about the problem.