What is the campaign queue showing?
What is the first flow step of these "low priority" triggered smart campaigns?
You might want to escalate on support.
And also, what is you pod?
We’ve experienced in the past. Definitely worth opening a support ticket.
- was a campaign accidentally built to be an infinite loop? For example Campaign A triggers off of Event A and caused Event B. Campaign B then triggers off of Event B and causes Event A, and the cycle continues.
- did you just have a large email campaign go out, or do a large list import? We used to experience trigger backlogs when doing imports of more than a hundred people or so and I had to restructure the campaigns which handle new records in order to reduce that problem.
Take a look at your Campaign Queue and see if there is any campaign that is running a high number of records that shouldn't be. Also, talk to your SFDC Admin and see if they changed anything that would cause that campaign to over-run.
We once had a HUGE backlog in the Campaign Queue because of a change in SFDC. We have a Marketo smart campaign to normalize Country to ISO 2-digit in case a record slips in (like through a list upload) with a non-standard value. Our SFDC Admin messed up a trigger in SFDC that for some reason changed Country to full country name. So records started ping-ponging back and forth between systems, and our normalization smart campaign clogged up the queue.