MemCached Bucket Failed partially to get and set after restart/rebalance/failover

4 node cluster running situational test (restart,failover,rebalance) against mem cached bucket

1. During the ramp stage the set and get ops works fine
2. Runs Change Phase
3. During rebound, there are only half of the data gets inserted, I don't see any errors on sets from the logs, and there is no exceptions return for sets ops.
For gets ops, operations status returns fail and returns message "not found" or "ERR_NOT_FOUND".

I am seeing this against different versions of couchbase server (2.2, 2.5, 4.0)