The workflow was published and added to the Document Library which appeared to be working correctly. The updates were updated but after a few times of running errors occurred and the workflow failed. These were reported as:
"The workflow could not update the item, possibly because one or more columns for the items require a different type of information"
After investigating why this was happening including checking my field names and types as well as building on a separate test environment and replicating the problem the resolution came about with building the workflow in a different way.
The failed workflow step we were using was ‘Update List Item’ option and this is when the error occurred. I was updating a number of fields in my current item as once which seemed the logical way to do this. But changing this to separating out the update steps and using the ‘Set Field in Current Item’ for each update resolved the error.
This may seem obvious but the logic says ‘Update List Item’ should work although it seems to put a lock that causes further updates to fail whereas ‘Set Field in Current Item’ works in a more sequential way preventing problems.