Membership 2 Activation Causes Site Failure

Good Afternoon (PST),

I have Membership installed along with a collection of other plugins. Recently, after making some updates, Membership 2 failed, causing complete render failures & other WPMU plugin failures.

ERRORS:

The errors I receive (& any user will likely receive) are: “Cannot modify header information – headers already sent”, “Permission denied”, “Cannot send session cache limiter – headers already sent”

ATTEMPTED RESOLUTION:

I have disabled security plugins, and disabled, uninstalled, & reinstalled Membership 2.

LOGS:

Here are some of the few browser provided errors in full (minus complete paths):

Warning: session_start(): open(/tmp/sess_vuExjB5A,2Sp67basEicO1, O_RDWR) failed: Permission denied (13) in [FULL PATH ABBREVIATED]/plugins/membership/lib/wpmu-lib/inc/class-thelib.php on line 145

Warning: session_start(): Cannot send session cache limiter – headers already sent (output started at [FULL PATH ABBREVIATED]/plugins/membership/lib/wpmu-lib/inc/class-thelib.php:145) in [FULL PATH ABBREVIATED]/plugins/membership/lib/wpmu-lib/inc/class-thelib.php on line 145

Warning: session_start(): open(/tmp/sess_vuExjB5A,2Sp67basEicO1, O_RDWR) failed: Permission denied (13) in [FULL PATH ABBREVIATED]/plugins/membership/lib/wpmu-lib/inc/class-thelib.php on line 145

Warning: session_start(): open(/tmp/sess_vuExjB5A,2Sp67basEicO1, O_RDWR) failed: Permission denied (13) in [FULL PATH ABBREVIATED]/plugins/membership/lib/wpmu-lib/inc/class-thelib.php on line 145

Warning: session_start(): Cannot send session cache limiter – headers already sent (output started at [FULL PATH ABBREVIATED]/plugins/membership/lib/wpmu-lib/inc/class-thelib.php:145) in [FULL PATH ABBREVIATED]/plugins/membership/lib/wpmu-lib/inc/class-thelib.php on line 145

Warning: Cannot modify header information – headers already sent by (output started at [FULL PATH ABBREVIATED]/plugins/membership/lib/wpmu-lib/inc/class-thelib.php:145) in [FULL PATH ABBREVIATED]/plugins/wpmudev-updates/includes/class-wpmudev-dashboard-site.php on line 468

Warning: Cannot modify header information – headers already sent by (output started at [FULL PATH ABBREVIATED]/plugins/membership/lib/wpmu-lib/inc/class-thelib.php:145) in [FULL PATH ABBREVIATED]/wp-includes/pluggable.php on line 1167

Warning: Unknown: open(/tmp/sess_vuExjB5A,2Sp67basEicO1, O_RDWR) failed: Permission denied (13) in Unknown on line 0

Warning: Unknown: Failed to write session data (files). Please verify that the current setting of session.save_path is correct (/tmp) in Unknown on line 0