We are trying to move our traditional master-slave Solr configuration to SolrCloud. As our index size is very small (around 1 GB), we are having only one shard. 
So basically, we are having same master-slave configuration with one leader and 6 replicas. 
We are experimenting with maxTime of both AutoCommit and AutoSoftCommit. Currently, autoCommit maxTime is 15 minutes and autoSoftCommit is 1 minute (Let me know if these values does not make sense). 

Caches are set such that warmup time is at most 20 seconds.

We are having continuous indexing requests mostly for updating the existing documents. Few requests are for deleting/adding the documents. 

The problem we are facing is that we are getting very frequent NullPointerExceptions.
We get continuous 200-300 such exceptions within a period of 30 seconds and for next few minutes, it works fine.

I am not sure what would be causing it. My guess, whenever, it is trying to replay tlog, we are getting these exceptions. Is anything wrong in my configuration?