I’ve been seeing these errors in our logs for a bit, and finally tracked it down:
PHP Warning: Invalid argument supplied for foreach() in /var/www/wp-content/plugins/events-calendar-pro/src/Tribe/Recurrence/Meta.php on line 884
I was able to trigger this by calling Tribe__Events__Pro__Recurrence__Meta::get_recurrence_for_event() on an event that had no exclusions saved in post meta. Once I saved an exclusion for that event, I was able to call that with no error. When I removed that exclusion, there appears to be an empty exclusion list stored in post meta, so the error is no longer shown.
There should probably be a check to make sure that $recurrence_meta[ $rule_type ] is available when $rule_type is “exclusions”, similar to the one already done for “rules” just above.

Thanks!