Problem

These errors have been thrown in traces:

ERROR 2016/10/13 10:35:26.659 Couldn't locate a schema from the cached Resource Set for location: 'null', namespace: {http://xxxxxx}
ERROR 2016/10/13 10:35:26.659 Couldn't locate a schema from the cached Resource Set for location: 'null', namespace: {http://xxxxx}

Resolution

Re-synchronize all web services for this instance