InnoDB MySQL table with a trigger that inserts into a MyISAM table
Inserting into a MyISAM table may take a table lock on that table.  Since that INSERT is coming from a Trigger on a InnoDB table, it is inside a transaction.  So, if the table lock takes a long time, the transaction takes a long time, hence "lock wait timeout".

The exception on the table lock is if there have been no updates or deletes from the MyISAM table and the PK is AUTO_INCREMENT.  (Or something like that.  Dig in the docs for the specifics.)

Is it possible to add to audit outside the InnoDB transaction?

You say "full table lock requests" -- which table?  What is the specific text?

Another thing that can mess up inserting a MyISAM table -- a big SELECT.  Perhaps you do a big 'report' twice a day?

Rethink whether to use MyISAM for audit.