Error: "ORA-01405: fetched column value is NULL. [sp_tconf/12959]" (4216041)

Error received during activation on a 3 node RAC:

"Error: Failed to find information about which instance is active. ORA-01405: fetched column value is NULL. [sp_tconf/12959]"

SQL> select thread#, status, groups, instance from gv$thread;
1 OPEN 4 HLPMTA
2 OPEN 4 HLPMTB
3 OPEN 4 HLPMTC
4 CLOSED 4

select instance_number, host_name from gv$instance;
1 HLPMTA
3 HLPMTC
2 HLPMTB

A thread is closed and is disabled as seen from v$thread.

1. Remove the thread 4 from RAC.

NOTE: For instruction on how to remove a node from RAC, contact Oracle Support.

2. Activate config.

You should see:
SQL> select thread#, status, groups, instance from gv$thread;
1 OPEN 4 HLPMTA
2 OPEN 4 HLPMTB
3 OPEN 4 HLPMTC

select instance_number, host_name from gv$instance;
1 HLPMTA
3 HLPMTC
2 HLPMTB

RAC