I have been doing some literature search on the subject of errors made by medical interpreters, be it ad hoc or hospital interpreters with little or no training. I found a paper that I thought you might find interesting and relevant, and it perhaps could even be used as a complement to your curriculum. It provides examples of the most common errors committed by those serving as interpreters. I think it is extremely illustrative. I have enclosed it as an attachment.
Submitted by Iris Mónica Vargas