expert advice needed for using memcached with php7

hi,

i am having issues with using php 7 with memcached and numerous tickets to my host still cannot solve the issue.
neither can they replicate the issue on their test sites or provide the root cause.
it seems to be happening on my account alone apparently.

so basically i am reaching out here hoping someone may recognize the errors and offer a solution.

hosted on SiteGround "Cloud" (not shared) they have 3 levels of caching - screenshot 0
the third of which is memcached.
the first 2 levels work fine.
i always get the following error when activating memcached in wp admin (screenshot 1)

Fatal error: Uncaught Error: Class 'Memcache' not found in /home/randal53/public_html/wp-content/plugins/sg-cachepress/class-sg-cachepress-memcache.php:177 Stack trace: #0 /home/randal53/public_html/wp-content/plugins/sg-cachepress/class-sg-cachepress-admin.php(215): SG_CachePress_Memcache->check_and_create_memcached_dropin() #1 /home/randal53/public_html/wp-includes/plugin.php(525): SG_CachePress_Admin->update_parameter('':wink: #2 /home/randal53/public_html/wp-admin/admin-ajax.php(89): do_action('wp_ajax_sg-cach...':wink: #3 {main} thrown in /home/randal53/public_html/wp-content/plugins/sg-cachepress/class-sg-cachepress-memcache.php on line 177

if i use "php variables manager" in cpanel and add 512M of memory_limit i get errors in wp admin at the top of the screen as well as seemingly different errors in the plugin again (screenshot 2 & 3).

the plugin used is theirs ;
https://wordpress.org/plugins/sg-cachepress/

now i have followed their tutorials precisely !!!
https://www.siteground.com/tutorials/supercacher/wordpress_memcached.htm

i have tried using php manager in cpanel to place php7 in the root of the folder as well as /public_html and no difference.
php 5.6 works fine with all 3 levels

i have tried applying php7 after enabling memcached, before every which way.
is it possible to interrupt the errors provided to come to a solution ?

any kind assistance in this would be greatly appreciated,
kind regards.