Hi Olivier,
What I could suggest is to check following points:
1. Check the BLS that has failed.
2. Check the input and intermediate formation, or if the BLS is retrieving data from some other sources.
com.sap.lhcommon.exceptions.EvaluationException - the error mostly comes when some incoming data has a special/unexpected character that has not been properly handled.
Hope it helps!
Best Regards,
Swaroop