cron trigger sending dozens identical instances of the same notification

I have accross a problem that I can not debug on my own. I am wondering if anyone has seen anything similar.

Two third-party plugins are using cron trigger to send out notifications. When triggered, cron sends out dozens (and sometimes hundreds) of identical notifications.

Notifications are sent via phpmailer (no smtp, elgg defaults overridden).

I can't identify the cause for the problem. I am doubting that the fault is within third-party plugins.

Elgg 1.7.8 (2010071002)

I would appreciate any guess/tips you might have.