In the meantime I’ve installed Elementor v3.1.0 and v1.9.2 of the plugin. In the logs I now see the underneath errors.
The class that fails to open does exist:
class-freemius.php 2021-01-27 18:37 932.0 KB rw- r– r–
PHP Fatal error: require_once(): Failed opening required '/var/www/vhosts/vbsdebrongooik.be/httpdocs/wp-content/plugins/addon-elements-for-elementor-page-builder/freemius/includes/class-freemius.php' (include_path='.:') in /var/www/vhosts/vbsdebrongooik.be/httpdocs/wp-content/plugins/addon-elements-for-elementor-page-builder/freemius/require.php on line 49
PHP Notice: require_once(): read of 567632 bytes failed with errno=14 Bad address in /var/www/vhosts/vbsdebrongooik.be/httpdocs/wp-content/plugins/addon-elements-for-elementor-page-builder/freemius/require.php on line 49