I have noticed that many of my switches that are in a stack are appearing numerous times in the switch stack member list. The model, serial, and MACs are all the same. There are only two switches in this stack but they appear 17 times each. It happens more often than not and makes the inventory report much larger than it should be.
Is this the built in switch stack resources for Cisco switch stacks, or something else that you've created? I had a similar issue with a custom resource that I did for Aruba switch stacks where the stacks were polled with a Universal Device Poller. The issue was with my query. If what you are seeing is something similar, I can try to dig up that query.