[Atlassian support]: 'Step exceeded processing limits and has timed out' can mean the concatenated names and values of all Workspace, Repository, and Deployment variables exceed 120,000 characters. The build hangs in a queued state or times out after 2 hours. Concatenate them and check the total: remove variables or shorten very long values. Secured variable values cannot be read back from the UI or API, so you need to know their values. If the total is under the limit and it still fails, raise a support ticket.

Context: A build that hangs for 2 hours then times out can be a variable-size limit, not a hung script.