Where is the source database configured for project_issue.migrate.inc?

I'm trying to migrate from project_issue on D6 to project_issue on D7, and not having any luck.

It seems that project_issue.migrate.inc is using the same database as both the source and the destination (or something along those lines). When trying to run the various migrations, I get errors that indicate it can't find database tables the I've confirmed exist in the old D6 database; that database is configured as "old" in the settings.php in the databases array (and works for Commerce/Ubercart migration), and has been configured in the migrate_d2d_ui and also works there (by some definition of "works", it's buggy as hell, but does find the old data and does things with it).

So, how do I tell the project_issue migrate code to use the old database?

Edit: Specifically, when running the ProjectIssueRethreadIssueFollowups migration, it gives this error (sofresh_drupal is the default db, I see no indicate it is looking at sofresh_old, the D6 database, at all):

Initialized Drupal 7.39 root directory at /home/sofresh/public_html     [notice]
Initialized Drupal site default at sites/default                        [notice]
Executing: mysql --defaults-extra-file=/tmp/drush_riB1oH --database=sofresh_drupal --host=localhost --silent  < /tmp/drush_q56GYr
Importing 'ProjectIssueRethreadIssueFollowups' migration                [notice]
exception 'PDOException' with message 'SQLSTATE[42S02]: Base table or[error]
view not found: 1146 Table
'sofresh_drupal.drupal_project_issue_comments' doesn't exist' in
/home/sofresh/public_html/includes/database/database.inc:2171
Stack trace:
#0 /home/sofresh/public_html/includes/database/database.inc(2171):
PDOStatement->execute(Array)
#1 /home/sofresh/public_html/includes/database/database.inc(683):
DatabaseStatementBase->execute(Array, Array)
#2 /home/sofresh/public_html/includes/database/database.inc(2350):
DatabaseConnection->query('UPDATE {comment...', Array, Array)
#3
/home/sofresh/public_html/sites/all/modules/project_issue/includes/project_issue.migrate.inc(118):
db_query('UPDATE {comment...')
#4
/home/sofresh/public_html/sites/all/modules/migrate/includes/base.inc(1073):
ProjectIssueRethreadIssueFollowupsMigration->import()
#5
/home/sofresh/public_html/sites/all/modules/migrate/migrate.drush.inc(1234):
MigrationBase->processImport(Array)
#6 [internal function]: drush_migrate_import('ProjectIssueRet...')
#7
/home/sofresh/.composer/vendor/drush/drush/includes/command.inc(368):
call_user_func_array('drush_migrate_i...', Array)
#8
/home/sofresh/.composer/vendor/drush/drush/includes/command.inc(219):
_drush_invoke_hooks(Array, Array)
#9 [internal function]: drush_command('ProjectIssueRet...')
#10
/home/sofresh/.composer/vendor/drush/drush/includes/command.inc(187):
call_user_func_array('drush_command', Array)
#11
/home/sofresh/.composer/vendor/drush/drush/lib/Drush/Boot/BaseBoot.php(62):
drush_dispatch(Array)
#12 /home/sofresh/.composer/vendor/drush/drush/drush.php(70):
Drush\Boot\BaseBoot->bootstrap_and_dispatch()
#13 /home/sofresh/.composer/vendor/drush/drush/drush.php(11):
drush_main()
#14 {main}
Command dispatch complete                                               [notice]