Enabling CB system plugin results in dead site/PHP errors

Site www.renownrepulse.com hosted by CloudAccess.

Using Joomla 3.8.5 with PHP 5.6.33 (trying to use any higher PHP version results in "Warning: Declaration of getcbrecaptchaTab::getDisplayRegistration($tab, $user, $ui) should be compatible with cbTabHandler::getDisplayRegistration($tab, $user, $ui, $postdata) in /mnt/data/vhosts/casite-426627.cloudaccess.net/httpdocs/components/com_comprofiler/plugin/user/plug_cbrecaptcha/cbrecaptcha.php on line 0" when viewing the CB configuration backend and "Error: Call to a member function init() on null: The memcache Cache Storage is not supported on this platform." when trying to load the front end of the site).

CB version: 2.1.3+build.2018.02.19.19.51.48.2dffa411d (the latest version at the time of writing)
CB Subs 4.1.1+build.2018.02.07.22.05.19.7f188e079 installed, also the latest version.

I had to get CA support to disable the CB system plugin because I was getting errors on both the front end and admin backend of the site such as:

Parse error: syntax error, unexpected '$z36e2db7' (T_VARIABLE) in /mnt/data/vhosts/casite-426627.cloudaccess.net/httpdocs/plugins/system/communitybuilder/communitybuilder.php on line 1

If I re-enable the CB system plugin then the same error immediately reappears as soon as I save the configuration in the admin backend. I noticed CB Subs was complaining that a few plugins were installed but not published, so I published them and tried publishing the CB System Plugin again, with the same result (and error).

For context: I recently did a comprehensive upgrade on this site from Joomla 2.5.28 to 3.8.5 including updating all plugins to their latest versions. This included CB and CB Subs. After I performed the upgrade the site worked (with the exception of one broken piece of CB/CB Subs functionality that I could live with temporarily, namely that user registration links result in "You are not authorized to view this page!"). So, job done, I left the site alone for a few days, doing nothing to it and not installing anything else or upgrading anything else. I then got notifications last week that the site wasn't working and had to get CA support to help, which they did by disabling the CB system plugin and the site immediately came back to life.

I am clueless in regards to this kind of PHP matter... Right now I have restored my site from a backup to keep it going and as such the CB system plugin is still disabled.

Using Joomla 3.8.5 with PHP 5.6.33 (trying to use any higher PHP version results in "Warning: Declaration of getcbrecaptchaTab::getDisplayRegistration($tab, $user, $ui) should be compatible with cbTabHandler::getDisplayRegistration($tab, $user, $ui, $postdata) in /mnt/data/vhosts/casite-426627.cloudaccess.net/httpdocs/components/com_comprofiler/plugin/user/plug_cbrecaptcha/cbrecaptcha.php on line 0" when viewing the CB configuration backend and "Error: Call to a member function init() on null: The memcache Cache Storage is not supported on this platform." when trying to load the front end of the site).

CB reCaptcha is not developed by us. Use CB AntiSpam for captcha (includes multiple captcha modes including reCaptcha). CB is tested on and compatible with PHP 7.1 and 7.2 so you can use either for better performance.

Parse error: syntax error, unexpected '$z36e2db7' (T_VARIABLE) in /mnt/data/vhosts/casite-426627.cloudaccess.net/httpdocs/plugins/system/communitybuilder/communitybuilder.php on line 1

That error makes no sense to me, sorry. That variable doesn't exist on line 1. Looks like CloudAccess is compressing PHP files? Contact CA regarding something like that as that should be disabled.