Self update for today - Found the cause of the slow execution. Mail outbound - was sending notifications - no problem, except 1.1.1.1 dns server was misbehaving today.

Suggestion: Maybe a capability in the cron script so that when it runs, if it detects its been active for more than x time, to exit and let the next instance of the cron script to send the next message... Possibly nicer way to handle delays like DNS failure for outbound mail. One execution run of cron.php was taking 6m18.617s