Fatal error EM v6.4.1 and WPFullCalendar stop working

Hi:

After update since EM 6.3 to EM 6.4.1. Fatal error in my website.

php Error log:

[13-Jun-2023 09:45:13 UTC] PHP Fatal error:  Uncaught TypeError: Cannot access offset of type string on string in /usr/home/xxxx.com/web/wp-content/plugins/events-manager/em-install.php:923
Stack trace:
#0 /usr/home/xxxx.com/web/wp-content/plugins/events-manager/em-install.php(42): em_upgrade_current_installation()
#1 /usr/home/xxxx.com/web/wp-content/plugins/events-manager/events-manager.php(619): em_install()
#2 /usr/home/xxxx.com/web/wp-includes/class-wp-hook.php(308): em_init('')
#3 /usr/home/xxxx.com/web/wp-includes/class-wp-hook.php(332): WP_Hook->apply_filters(NULL, Array)
#4 /usr/home/xxxx.com/web/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#5 /usr/home/xxxx.com/web/wp-settings.php(623): do_action('init')
#6 /usr/home/xxxx.com/web/wp-config.php(96): require_once('/usr/home/escri...')
#7 /usr/home/xxxx.com/web/wp-load.php(50): require_once('/usr/home/escri...')
#8 /usr/home/xxxx.com/web/wp-admin/admin-ajax.php(22): require_once('/usr/home/escri...')
#9 {main}
  thrown in /usr/home/xxxx.com/web/wp-content/plugins/events-manager/em-install.php on line 923

Also WPFullCalendar stop working and events arent shown anymore after update to EM6.4.1 , in EM 6.3 all works ok