Failing to insert into table getting error: ORA-00600: internal error code, arguments: [ktssinseg2]
You could try to copy the table into a new object:

CREATE TABLE newtab AS SELECT * FROM MV_IN_SMS_TOTAL 


Try to do your inserts into the new table. If that solves the problem and the problem is isolated to that specific object (table), and you use that as a workaround.

RENAME TABLE MV_IN_SMS_TOTAL TO MV_IN_SMS_TOTAL_OLD;
CREATE TABLE MV_IN_SMS_TOTAL AS SELECT * FROM MV_IN_SMS_TOTAL_OLD;


Note that all auxiliary objects must be created. Indexes, constraints, triggers, you name it - and privileges.

Regards,

Daniel