Hi Andrew,
Like Carl mentioned Tasks can sometimes fall behind. They can run into what we call concurrency problems as there is a limit of four jobs (including tasks) running at a time per app, as well as 14 per server.
One of the first things we recommend when people run into tasks backing up over each other is to stagger their times more like 15 minutes than 2 minutes apart. Do that and then please let us know at support@knack.com if something is still not working correctly in your task workflow.
You may also want to check out this other related post about tasks with dependencies on other tasks like yours. Linked tasks (task dependency)
It includes some good information from a Knack Expert and may help you know more about how our task system handles tasks.