woocommerce_variation_has_changed trigger is not reliable

Better to use
$(".variations_form .single_variation").on("show_variation hide_variation")

instead

$(".variations_form").on("woocommerce_variation_has_changed")

What is advantage of using another hook/event ? would be great to know about your finding so I will update the plugin.

The idea is simple – in case using AJAX (for finding the variation), hook 'woocommerce_variation_has_changed trigger' fires early then AJAX is finished. You can to test it with product with count of variations more than 30.
Follow to github by link above, we discussed about it.

Okay, That is great finding, I will surly update this.

Thanks for all the efforts.