Fatal error: add_off_pattern_flag_to_rule() must be of the type array

We’re getting a fatal error on the Edit Event page in Time and Date metabox:

PHP Fatal error:  Uncaught TypeError: Return value of TEC\Events_Pro\Custom_Tables\V1\Updates\Controller::add_off_pattern_flag_to_rule() must be of the type array, string returned in /mnt/data/home/XXXXXXXX.cloudwaysapps.com/XXXXXXXX/public_html/wp-content/plugins/events-calendar-pro/src/Events_Pro/Custom_Tables/V1/Traits/With_Event_Recurrence.php:430
Stack trace:
#0 /mnt/data/home/XXXXXXXX.cloudwaysapps.com/XXXXXXXX/public_html/wp-content/plugins/events-calendar-pro/src/Events_Pro/Custom_Tables/V1/Traits/With_Event_Recurrence.php(495): TEC\Events_Pro\Custom_Tables\V1\Updates\Controller->add_off_pattern_flag_to_rule()
#1 [internal function]: TEC\Events_Pro\Custom_Tables\V1\Updates\Controller->TEC\Events_Pro\Custom_Tables\V1\Traits\{closure}()
#2 /mnt/data/home/XXXXXXXX.cloudwaysapps.com/XXXXXXXX/public_html/wp-content/plugins/events-calendar-pro/src/Events_Pro/Custom_Tables/V1/Traits/With_Event_Recurrence.php(496): array_map()
#3 /mnt/data/home/XXXXXXXX.cloudwaysapps.com/XXXXXXXX/public_html/wp-content/plugins/events-calendar- in /mnt/data/home/XXXXXXXX.cloudwaysapps.com/XXXXXXXX/public_html/wp-content/plugins/events-calendar-pro/src/Events_Pro/Custom_Tables/V1/Traits/With_Event_Recurrence.php on line 430

We just completed a migration to the latest versions of 6.x from 5.x.