Slow errors from Membership 2 Pro plugin cause server to halt

Server (Flywheel) is getting hammered with M2PRO slow errors:

SLOW ERRORS
MOST COMMON SLOW ERROR (15 TIMES)
[pool site-98893] script_filename = /www//wp-admin/admin-ajax.php session_start() /www/wp-content/plugins/membership/lib/wpmu-lib/inc/class-thelib.php:145 _sess_init() /www/wp-content/plugins/membership/lib/wpmu-lib/inc/class-thelib.php:240 __construct() /www/wp-content/plugins/membership/lib/wpmu-lib/inc/class-thelib-core.php:89 __construct() /www/wp-content/plugins/membership/lib/wpmu-lib/core.php:106 get_obj() /www/wp-content/plugins/membership/lib/wpmu-lib/core.php:49 lib3() /www/wp-content/plugins/membership/app/class-ms-rule.php:1391 __get() unknown:0 get_rule() /www/wp-content/plugins/membership/app/model/class-ms-model-membership.php:1680 get_rule() /www/wp-content/plugins/membership/app/model/class-ms-model-membership.php:1422 prepare_obj() /www/wp-content/plugins/membership/app/class-ms-factory.php:231 prepare_obj() /www/wp-content/plugins/membership/app/class-ms-factory.php:152 load() /www/wp-content/plugins/membership/app/model/class-ms-model-membership.php:1002 _get_system_membership() /www/wp-content/plugins/membership/app/model/class-ms-model-membership.php:1042 get_base() /www/wp-content/plugins/membership/app/model/class-ms-model-plugin.php:458 load_rules() unknown:0 call_user_func_array() /www/wp-includes/class-wp-hook.php:298 apply_filters() /www/wp-includes/class-wp-hook.php:323 do_action() /www/wp-includes/plugin.php:453 do_action() /www/wp-content/plugins/membership/app/model/class-ms-model-plugin.php:144 init_member() unknown:0

Downgrading to version 1.0.3.4 didn't resolve the errors.