Unable to get the metrics from stacked devices through snmp exporter

Exporters and Metrics snmp_exporter
1

I have One primary device and two secondary devices. The secondary devices are stacked with primary one. When I do the snmpwalk on my primary , I am able to get the metrics for primary & all secondary devices . But in Prometheus by using snmp_exporter, its throwing the below errors,

* collected metric "Devicename" { label:<name:"DeviceMac" value:"0F:10:10:10:55:33" > gauge:<value:1 > } was collected before with the same name and label values
* collected metric "DeviceVersion" { label:<name:"DeviceMac" value:"0F:10:10:10:55:33" > label:<name:"DeviceVersion" value:"2.3.992.0" > gauge:<value:1 > } was collected before with the same name and label values
* collected metric "DeviceNumberBranches" { label:<name:"DeviceMac" value:"0F:10:10:10:55:33" > gauge:<value:3 > } was collected before with the same name and label values
* collected metric "DeviceotalPower" { label:<name:"DeviceMac" value:"0F:10:10:10:55:33" > gauge:<value:0 > } was collected before with the same name and label values

But when I remove the secondary devices and kept only the primary device, the Prometheus is collecting the primary metrics. How can I get the metrics when the devices are stacked?

Can someone please help to fix the issue.