VPS memory events and timeouts

A hosted VPS (AlmaLinux Apache with CPanel) is having memory timeouts crashing our WordPress site. Hosting support claims this is a PHPList issue. We have a list of less than 350 subscribers and send a campaign only once per week. The crashes are happening frequently and at anytime.

Process queue cron: */5 * * * *

Batch size, period and throttle:

define(‘MAILQUEUE_BATCH_SIZE’, 100);
define(‘MAILQUEUE_BATCH_PERIOD’, 600);
define(‘MAILQUEUE_THROTTLE’, 1);

It seems as if this shouldn’t be a demanding use of self hosted PHPList. Any insight or advice would be appreciated.