Couchbase operations are failing after couchbase server is restarted

When the couchbase server is stopped, we are receiving logs for attempting to reconnect to the couchbase.

Could not connect to endpoint on reconnect attempt 1523, retrying with delay 4096 MILLISECONDS:
Bucket not found on Select Bucket command 

After the server is started, we received logs that the bucket has been connected. This happens automatically

New Bucket bucket-name config proposed.
Completed refreshing config for bucket "bucket-name"

But after the bucket has opened, when any of the service endpoint is hit, it is not able to perform any couchbase operations even though the connection to bucket is established.
When trying it out in local, we got time out exception logs.

ExceptionAdvisor::METHOD => handleException :: MESSAGE => {"b":"bucket-name", s":"n1ql","t":75000000,"i":"10c731"}

and this resulted in 500 INTERNAL_SERVER_ERROR
When looking into the logs in env, we got null pointer exception

ExceptionAdvisor :: METHOD => handleException :: MESSAGE => null

Underlying problem: Even though the bucket is opened, after couchbase restart, it is not able to perform any operations. Any idea why this is happening and any solution regarding this?

Currently if the couchbase server is restarted or started after being stopped, we are restarting all the services since the operations fail and it needs to be restarted inorder to work properly. And after being restarted, it works properly.