Thank You very much for the feedback and suggestions, I greatly appreciate the help.
We implemented the above exclusions, and additionally during that process, Amalia E of WP Engine Technical Support was able to further successfully diagnose and rectify the issue.
The final solution was to add cache exclusions also for the WooCommerce plugin, which apparently has its own cache operation that we did not know about before.
Implementing the following cache exclusions , in addition to the previously already implemented exclusion of the wishlist page and YITH cookie, as well as enabling AJAX loading, fully solved the problem on mobile. Amalia E can be contacted through WP Engine Tech Support if further technical explanation is useful to YITH
woocommerce_cart_hash
wp_woocommerce_session_
woocommerce_items_in_cart
I would highly recommend that YITH would please add this information to the official documentation for the plugin. We spent over 30 hours attempting to resolve this issue.
We can now consider this problem closed at this time unless further issues emerge – thank you, Dan
