How do I find an invalid utf8 character "somewhere" in my MySQL/trac database
You could try turning on the general query log, which logs every query the server receives, and then use that information to see what's being queried, and then issue those queries yourself and examine the data.

To see the current setting for the general log (location and whether it's enabled):

mysql&gt; SHOW VARIABLES LIKE 'general_log%';  # shows the on/off status and file path


To turn it on:

mysql&gt; SET GLOBAL general_log = on; # or off to disable


Remember to turn if off again when you're done, to avoid filling the disk and potentially degrading performance with excessive I/O.

There are also options for logging to a table instead of a file.

mysql&gt; SHOW VARIABLES LIKE 'log_output';    # shows whether logging to FILE or TABLE