Memory Store Metrics Extraction Error

Start command:
./stackdriver_exporter --google.project-id $project --web.listen-address=:9259 --monitoring.metrics-type-prefixes redis.googleapis.com &

Error while querying redis/memorystore exporter:

[root@prometheus-vm04 stackdriver_exporter-0.5.1.linux-amd64]# curl localhost:9259/metrics
ERRO[0011] Error retrieving Time Series metrics for descriptor redis.googleapis.com/commands/calls: googleapi: Error 500: An internal error occurred., backendError source="monitoring_collector.go:176"
ERRO[0011] Error while getting Google Stackdriver Monitoring metrics: googleapi: Error 500: An internal error occurred., backendError source="monitoring_collector.go:132"
An error has occurred during metrics collection:

4 error(s) occurred:

• collected metric stackdriver_redis_instance_redis_googleapis_com_stats_cpu_utilization label:<name:"instance_id" value:"projects/vuclip-ubs-poc/locations/us-central1/instances/ubs-poc-redis" > label:<name:"node_id" value:"v1-usce1-ubs-poc-redis-736-0000" > label:<name:"project_id" value:"vuclip-ubs-poc" > label:<name:"region" value:"us-central1" > label:<name:"unit" value:"Cycles" > gauge:<value:0.08999999999991815 > was collected before with the same name and label values
• collected metric stackdriver_redis_instance_redis_googleapis_com_stats_cpu_utilization label:<name:"instance_id" value:"projects/vuclip-ubs-poc/locations/us-central1/instances/ubs-poc-redis" > label:<name:"node_id" value:"v1-usce1-ubs-poc-redis-736-0000" > label:<name:"project_id" value:"vuclip-ubs-poc" > label:<name:"region" value:"us-central1" > label:<name:"unit" value:"Cycles" > gauge:<value:0 > was collected before with the same name and label values
• collected metric stackdriver_redis_instance_redis_googleapis_com_stats_cpu_utilization label:<name:"instance_id" value:"projects/vuclip-ubs-poc/locations/us-central1/instances/ubs-poc-redis" > label:<name:"node_id" value:"v1-usce1-ubs-poc-redis-736-0000" > label:<name:"project_id" value:"vuclip-ubs-poc" > label:<name:"region" value:"us-central1" > label:<name:"unit" value:"Cycles" > gauge:<value:0.049999999999954525 > was collected before with the same name and label values
• collected metric stackdriver_redis_instance_redis_googleapis_com_stats_network_traffic label:<name:"instance_id" value:"projects/vuclip-ubs-poc/locations/us-central1/instances/ubs-poc-redis" > label:<name:"node_id" value:"v1-usce1-ubs-poc-redis-736-0000" > label:<name:"project_id" value:"vuclip-ubs-poc" > label:<name:"region" value:"us-central1" > label:<name:"unit" value:"By" > gauge:<value:290193 > was collected before with the same name and label values

Reproduce the reported command and curl localhost:9259/metrics, then inspect monitoring_collector.go at the logged lines 132 and 176. Determine why the Redis/MemoryStore query returns a backend error and why duplicate metrics are collected; done means the endpoint collects these metrics without those errors.