Mautic Import Frozen

Your software
My Mautic version is: Latest Version
My PHP version is: PHP Version 7.2.24-0ubuntu0.18.04.1

Your problem
My problem is:

All of a sudden my imports stopped working. Trying to import a small file with two columns, Email & Stage

These errors are showing in the log:
[2019-11-12 07:02:55] mautic.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\FatalThrowableError: “Call to a member function getId() on null” at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php line 625 {“exception”:"[object] (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0): Call to a member function getId() on null at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php:625)"}
[2019-11-12 07:04:10] mautic.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\FatalThrowableError: “Call to a member function getId() on null” at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php line 625 {“exception”:"[object] (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0): Call to a member function getId() on null at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php:625)"}
[2019-11-12 07:04:14] mautic.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\FatalThrowableError: “Call to a member function getId() on null” at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php line 625 {“exception”:"[object] (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0): Call to a member function getId() on null at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php:625)"}
[2019-11-12 07:13:42] mautic.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\FatalThrowableError: “Call to a member function getId() on null” at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php line 625 {“exception”:"[object] (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0): Call to a member function getId() on null at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php:625)"}
[2019-11-12 09:03:27] mautic.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\FatalThrowableError: “Call to a member function getId() on null” at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php line 625 {“exception”:"[object] (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0): Call to a member function getId() on null at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php:625)"}
[2019-11-12 09:11:06] mautic.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\FatalThrowableError: “Call to a member function getId() on null” at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php line 625 {“exception”:"[object] (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0): Call to a member function getId() on null at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php:625)"}
[2019-11-12 09:11:22] mautic.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\FatalThrowableError: “Call to a member function getId() on null” at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php line 625 {“exception”:"[object] (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0): Call to a member function getId() on null at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php:625)"}
[2019-11-12 09:11:25] mautic.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\FatalThrowableError: “Call to a member function getId() on null” at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php line 625 {“exception”:"[object] (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0): Call to a member function getId() on null at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php:625)"}
[2019-11-12 09:11:58] mautic.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\FatalThrowableError: “Call to a member function getId() on null” at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php line 625 {“exception”:"[object] (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0): Call to a member function getId() on null at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php:625)"}
[2019-11-12 09:12:47] mautic.CRITICAL: Uncaught PHP Exception Symfony\Component\Debug\Exception\FatalThrowableError: “Call to a member function getId() on null” at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php line 625 {“exception”:"[object] (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0): Call to a member function getId() on null at /var/www/mautic/app/bundles/LeadBundle/Model/LeadModel.php:625)"}

Steps I have tried to fix the problem:
Tried running Mautic:import
Tried clearing cache in /app/cache

I have run some tests, ran a different import with different fields and all worked fine. Problem seems to be with the field stage.