I have always worked on the applications side but I am looking at the RD of a report to try and an error check (dev is on holiday) and trying to see how "fetch" works. I know SQL but have not used it ever as a query.

Do you have a debuglog of the problem?

Or do you have any workcentre messages?. If so open F01131M in databrowser
ZMAN9 is your AN8 and ZMDTI = date job ran.
Scroll over to ZMFCTNM and ZMLNBR. This is where your errors are coming from

Fetch works as a simple query, it means it looks only to a single value of data. There are 2 options for this action "Fetch Single" and "Fetch Next".

Fetch single, will only let you receive an individual value of your query (Like Select SomethingA, SomethinB from TableA WHERE Data1="Unique"), letting you with only 1 row of data.

Fetch Next, it's used alongside with a "Select" statement, where you can retrieve more than one row of data (multiple values defined on the Where Sentence on a standard SQL query).

Hope this help