hI @a_b_se,
I would recommend checking all your JS code parts first, normally this errors throw because there is something missing in content blocks, personalization blocks, delivery names.
If it seems correct to you, and as your are saying it happens inconsistently I would recommend opening a ticket to Adobe Support. I recently experienced a similar case on a project where deliveries where randomly failing, and in the end, it turned out to be an Adobe Campaign bug. So don't hesitate to write them if you are confident with your code.
If you need something more, happy to help!
Best,
Celia