SEMS ERROR: error/unexpected reply from redis: 'Too many registrations

Would you be able to tell me the right SEMS configuration in a Master-Slave setup, please?

We have had initially SEMS write to single master redis-server only and replication to slaves, but we faced some challenges with this setup:
A. If the master Redis-server fails, there would be no failover and this will stop SIP REGISTER
B. We have two zones, if the network link between the zones breaks, then one zone will face SIP outage with new or expired SIP REGISTER as it won’t be able to reach master Redis-server due to network outage