Sorry for inconvenience.
There was weird error on some servers. Some pool servers created wrong DAG file for that period.
After flushing DAG file and restart, it is solved and working well.
I'm investigating the issue that how come this issue can happen.
i had that same issue a couple of days ago and i was away from my miner and busy....i lost 8 hours of mining
please investigate what is the root cause of the problem and solve it
Best Regards