Well, as the error message tells you, there seems to be some problem with your Redis server. You should look into the server logs for any errors related to Redis. One possible reason could be that you need to allocate a larger amount of memory to the Redis instance. Probably what happens when you refresh, the Redis instance have already restarted and that is why it is working again.
Do you run everything on the same server, or do you have a separate server for Redis? If the latter is the case the problem could also be due to an unreliable network connection between the two servers.