Calcuated field disappears halfway through signatures - Business account

We have a group business account, and use a couple templates/workflows for our expense approvals and employee travel approvals. The purchasing expense approval works well, but the travel does not. The field that has issues is a calculated field, which totals other numbered fields and calculated fields. When the form filler completes the document, this field is visible and totals correctly. We require 4 signatures on each document, and during this signature process, this 'total' calculated field is lost. It is the only field to disappear.

When I remove all the other emails from the workflow and just use my email, the document works perfectly. It's only when additional emails are included on the workflow does the problem arise. Please advise, any help would be greatly appreciated!