What is the best way to solve common error such load balancing and login issue ?

Will try to answer this to the best of my knowledge. Bro, please double check all the specs of your hardware meets, if not exceeds, SAPs minimum system requirements. Also, verify your network connections, specially the wired ones. Poor conductivity could result in lower signal strength or loss. Most probably you're implementing a firewall appliance, please do check that too if the configurations are in favor of SAP users.