Error in REST API calls to get Policy List and Catalog Images

Dear Fiends, I am getting correct data in REST API calls while calling for JOB List (admin/jobs) or host list (/config/hosts) however receving below error while trying to get policy list(config/policies) or catalog images(catalog/images).

{"errorCode":25,"errorMessage":"cannot connect on socket"}

some logs from nbwebservice unified logs:

0,51216,495,495,2028,1548546458610,20145,58,0:,60::getConnection() - connecting to service BPDBM on port 13721,53:com.netbackup.common.web.dao.socket.ConnectionManager,1 2,51216,495,495,2029,1548546458623,20145,58,0:,94::getConnection() - received java.net.ConnectException: Connection refused (Connection refused),2,(0|) 2,51216,495,495,2030,1548546458623,20145,58,0:,53::getConnection() - failed to connect to service BPDBM,2,(0|) 2,51216,495,495,2031,1548546458623,20145,58,0:,56:[NBDaoException] - Code:25 Msg:cannot connect on socket,1,(0|) 2,51216,495,495,2032,1548546458623,20145,58,0:,76:com.netbackup.common.web.dao.socket.NBDaoException: cannot connect on socket,2,(0|)

I am not sure why its working for some requests and for some its not working.

Please help me with this.

Regards Anwar