I would suggest adding the following (at the top of your script) for debugging:

use strict;
use warnings;
use Carp;

# other use statements here...

$SIG{__DIE__} = sub { Carp::confess @_ };

# remainder of your code here...
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I would then run the code. The Carp::confess will (effectively) give you a full stack trace of calls when the die() occurred. You can then see where your script was when the error occurred.

My hunch is that when your Net::SFTP connection failed and the program exited (error 1), error 2 was generated because the database handle was destroyed (forcing the rollback) with no disconnect.

You may want to consider opening the database connection after you have the SSH/SFTP connection completed, using a signal handler to clean up the database handle if an error occurs, or change the way the database connection is created (although I doubt that one is what you want).

Hope that helps.