Trigger interval for timer events

I’m noticing now that our timer trigger, to track how long a user was on a page, was been firing after 3 seconds, 6 seconds, and 9 seconds, rather than 30, 60, and 90 seconds. Only one trigger would properly, where the trigger interval was set to “30000” instead of the default “3000”.

Can anyone else speak to this in terms of trigger intervals of 3000 firing after 3 seconds instead of 30? Does anyone else have the interval set to 30000 for 30 seconds? How is the trigger interval built for Matomo?

Any help here would be much appreciated.