Event Tickets (v4.11.5+): Override the maximum quantity allowed to be purchased in a single Add To Cart action.

functions.php

<?php
/**
 * Event Tickets (v4.11.5+): Override the maximum quantity allowed to be purchased in a single Add To Cart action.
 *
 * @link https://gist.github.com/cliffordp/d5254fa306fa0c4ec1a27e73a083755e This snippet.
 * @link https://theeventscalendar.com/knowledgebase/k/settings-overview-event-tickets-and-event-tickets-plus/#Ticket_settings Help article.
 *
 * @param Tribe__Tickets__Ticket_Object $ticket              Ticket object.
 * @param WP_Post                       $event               Event post.
 * @param int                           $ticket_id           Raw ticket ID.
 * @param int                           $available_at_a_time Max purchase quantity, as restricted by Max At A Time.
 *
 * @return int
 */
function cliff_change_max_qty_able_to_add_to_cart_at_a_time(
	$available_at_a_time,
	$ticket,
	$event,
	$ticket_id
) {
	if ( 12345 === $event->ID ) {
		$available_at_a_time = 180;
	}

	return $available_at_a_time;
}

add_filter( 'tribe_tickets_get_ticket_max_purchase', 'cliff_change_max_qty_able_to_add_to_cart_at_a_time', 10, 4 );