We can see from below that you've tweaked and disabled many of the memory "safety valve" and other memory related settings. 
Agree. 
Also you are running with JVM heap size of 3.81GB which is non default. For a 16GB node I would expect 8GB. 

Try restoring the yaml values to the defaults and allowing the cassandra-env.sh file to determine the memory size. 

Cheers
 
-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton

On 5/04/2013, at 12:36 PM, Bryan Talbot <btalbot@aeriagames.com> wrote:

On Thu, Apr 4, 2013 at 1:27 AM, <adeel.akbar@panasiangroup.com> wrote:

After some time (1 hour / 2 hour) cassandra shut services on one or two nodes with follwoing errors;


Wonder what the workload and schema is like ...

We can see from below that you've tweaked and disabled many of the memory "safety valve" and other memory related settings.  Those could be causing issues too.

 
hinted_handoff_throttle_delay_in_ms: 0
flush_largest_memtables_at: 1.0
reduce_cache_sizes_at: 1.0
reduce_cache_capacity_to: 0.6
rpc_keepalive: true
rpc_server_type: sync
rpc_min_threads: 16
rpc_max_threads: 2147483647
in_memory_compaction_limit_in_mb: 256
compaction_throughput_mb_per_sec: 16
rpc_timeout_in_ms: 15000
dynamic_snitch_badness_threshold: 0.0