Found the root cause.

Redisson was adding extra characters while encoding https://redisson.pro/docs/data-and-services/data-serialization/?utm_source=chatgpt.com

Plain text codec works

config.setCodec(new StringCodec());
        config.useSingleServer()
                .setAddress(redisURL)
                .setConnectionPoolSize(30);
        RedissonClient redisson = Redisson.create(config);