Hello @alxwdm and welcome to the KNIME community!
The easiest way would be to put the entire loop body into a try-catch block. I started building that, but then I figured you might not want to write the csv files in case of a failure? In the screenshot below you’ll find the general application of a Try-Catch block. The fallback table is mandatory.
What parts of the loop do you expect to fail? I can see 3 parts (reading, manipulation, writing) in each branch and depending on where something might go wrong, and what you want to do in that case, the solution will be different.
Or in more simpler terms: Are you fine with writing only one of the files, or would you rather have both or none?