My company network is very unstable. It takes so much time to ping to gateway about 50ms or higher. I did some troubleshoot to find out the cause. I have to try arp-scan when network is unstable and see many duplicate IP with same MAC address. This is a section of output:

I ran an arp-scan to detect any ip address conflict in the network. The output as seen below:

192.168.x.91 02:a0xx:d6:64 (Unknown)

192.168.x.91 02:a0xx:d6:64 (Unknown) (DUP: 2)

Please note the (DUP :2)

What does the o/p describes, showing duplicate for same ip and mac address. How can that be a duplicate?

How are IPs assigned on your company network? You have issues. There should never be a duplicate of an IP. Somebody probably has a fixed IP that's conflicting. Thank them for keeping you in work ;-).