SPM sql plan baseline purge error

Hi,

Oracle 12.2 EE on Linux 7

I found the SPM auto purge of baselines was not functioning and followed the manual purge routine to try and get things cleaned up.  After running for 40 minutes I get an error and no baselines have been dropped.

VARIABLE ret NUMBER;
BEGIN
:ret := sys.dbms_spm_internal.auto_purge_sql_plan_baseline;
END;
/

PRINT ret;

SQL>   2    3    4
BEGIN
*
ERROR at line 1:
ORA-31011: XML parsing failed
ORA-19213: error occurred in XML processing at lines 1
LPX-00231: invalid character 48 ('0') found in a Name or Nmtoken
ORA-06512: at "SYS.DBMS_SPM", line 1210
ORA-06512: at "SYS.DBMS_SPM", line 314