Redis connection errors (session handling)

I am using Redis cache for session storage in my Magento 2.4.3-p2 based store.
The app/etc/env.php setting looks like

'session' => [
    'save' => 'redis',
    'redis' => [
        'host' => '<private-ip>',
        'port' => '6380',
        'password' => '',
        'timeout' => '5',
        'persistent_identifier' => '',
        'database' => '2',
        'compression_threshold' => '2048',
        'compression_library' => 'gzip',
        'log_level' => '3',
        'max_concurrency' => '12',
        'break_after_frontend' => '5',
        'break_after_adminhtml' => '30',
        'first_lifetime' => '600',
        'bot_first_lifetime' => '60',
        'bot_lifetime' => '7200',
        'disable_locking' => '0',
        'min_lifetime' => '60',
        'max_lifetime' => '2592000'
    ]
],

Note: Redis is installed in a separate instance connected via private IP

And, I am frequently seeing the below errors in my server logs

1. Warning: session_write_close(): Failed to write session data using user-defined save handler. (session.save_path: /var/lib/php/sessions)
2. Connection to Redis : failed after 1 failures.Last Error : (1) Connection refused
3. read error on connection to :

Redis (v6.0.9) installed on Ubuntu 18.04 instance has 32 GB of RAM and the settings look like this:

maxmemory:1gb
maxmemory_policy:allkeys-lru

New Relic graph

Any idea what could be the reason? and some debugging tips/tools?