Simon et al:
The change you made as stated in the following link and described below has broken the changed packages.
It would appear your developers made a change that assumes if the source Salesforce object has a SystemModStamp column then the SystemModStamp column must exist in all target objects for the given source object. This is a fatal assumption and we have packages that have not worked since this change was made.
This was reported yesterday (Monday, April 30, 2018) during our business hours in the Eastern Time Zone in the United States, and we have not heard back from you. It is urgent that you reply and your team reverts back to the old code / undoes the change.