Dis you also move to Oracle 12c?
It is a bug for Oracle, please see
https://community.oracle.com/message/12970776#12970776
As suggested by Oracle experts, it can be resolved by
Turning OFF the FIX_CONTROL will resolve the issue
The workaround is to set "_fix_control"='17376322:OFF'
SQL> alter session set "_fix_control"='17376322:OFF';
or at system level :
SQL> alter system set "_fix_control"='17376322:OFF';
OR
Apply Patch 19509982 if available for your DB Version and Platform
https://support.oracle.com/rs?type=patch&id=19509982
Can you please contact your DBA for making these changes and see if the problem is resolved .