Oracle Message LPX-00285 - invalid Unicode surrogate ~X ~X

ERRORinvalid Unicode surrogate ~X ~X
CAUSEA Unicode document contained an invalid surrogate. If the first (high) surrogate is in the correct range 0xD800 to 0xDBFF, then the second (low) surrogate must be in the range 0xDC00 to 0xDFFF.
ACTIONCorrect the document.