Thanks. But i saw this answer. In that case all the events older than a certain days were giving error.
but in my case only events from a certain time period are giving error. Events before that and after that are fine.
I am thinking this might be due to some issue with the buckets but I am having issues only with maybe 100 events only. So what would be the best way to fix these. I haven't tried the bucket repair command but that might take a long time.