IDOCFlatToXmlConvertor fails with exception java.lang.ArrayIndexOutOfBoundsException: -1

Hello,

We had a configuration working for Flat File IDOC to XML but it is failing now in development system (PI 7.11 dual stack) with:

java.lang.ArrayIndexOutOfBoundsException: -1

Maybe the source structure changed... Any ideas how can we more clearly see detail about the error?

I checked defaultTrace but didn't' find much:

Here is the Adapter Module config:

Again, this used to be working so I am mostly interested in help seeing more detail about the error.

Many thanks for your ideas!