When ACF and The Events Calendar both register/enqueue the same script (select2), there are conflicts. This should resolve the issue.

disable-tribe-select2-contextual.php

<?php
/**
 * Disable Tribe Select2 on non-tribe admin pages
 */
function _theme_disable_tribe_select2() {
	$screen = get_current_screen();

	if ( 'tribe_events' === $screen->id ) {
		return;
	}

	$tribe_post_types = array(
		'tribe_events',
		'tribe_venue',
	);

	if ( in_array( $screen->post_type, $tribe_post_types ) ) {
		return;
	}

	wp_deregister_script( 'tribe-select2' );
}

add_action( 'admin_enqueue_scripts', '_theme_disable_tribe_select2', 99 );