As per the error, the sem5.log may be corrupted. The log needs to be recreated.
Solution: http://www.symantec.com/docs/TECH167275
But the article mentioned in the above link (TECH96159) is not available anymore. However, you may try the solution mentioned in the article at the below link to recteate the log file.
http://www.symantec.com/docs/TECH178718
Note: in this article the version of dbsrv is 11. You will need to replace this version in the command with the one that is on your server.
Eg: dbsrv16 -f "D:\SEPM 12.1.6\db\sem5.db"