Duplicate MAC addresses for different devices

Why am I getting duplicate MAC addresses like those shown below?
The number of duplicates grows given an extended scanning time.
Note: the duplicates always include IP 192.168.0.130, which is a TP-LINK RE605 wireless extender.

192.168.0.29 66-E9-31-50-71-A0 ICMP 6 ms X01700AMEEDR.local The RPC server is unavailable. 0% 4%
192.168.0.97 66-E9-31-50-71-A0 ICMP 3 ms Denon-AVR-X2800H.local 80 The RPC server is unavailable. 0% 1%
192.168.0.130 66-E9-31-50-71-A0 ICMP 5 ms extender.net 80 The RPC server is unavailable. 0% 1%

Sometimes you may notice that Network Scanner reports one MAC address for all devices behind a wireless range extender or repeater. In this case it would look like those devices have different IP addresses, yet the same MAC address.

A range extender typically hides devices behind itself and does not retain their MAC addresses. It is not a bug in Network Scanner. You can type this line in a command prompt and observe the same behaviour:

arp -a

One way around this issue would be to enable the WDS mode (Wireless Distribution System). The advantage of WDS is that it preserves the MAC addresses of client frames across links between access points. The drawback of WDS is that devices from different vendors may not be compatible with each other.