What's the strange activity in the home router's DHCP statistics?

Question

DHCP

Recently, I noticed strange activity in the home router's DHCP statistics.
Asus RT-N13UU-B1 router. Firmware Wive-NG-RTNL latest (EOL). The network is configured for addresses in the range 192.168.1.* mask 255.255.255.0 /There are two phones and one tablet via WiFi, a Samsung smart TV, a laptop and a QNAP TS-251+ NAS on the wire. Only six clients.
In the DHCP statistics there is a list of randomly assigned addresses with arbitrary MACs. The addresses are not in order, but this is not a problem, but a feature of the firmware. Moreover, all addresses have the expired status, even if they were not there in the morning and already half a dozen in the evening. The screen is attached (a device without a shadow that is not expired - smart TV).
I immediately changed the password in the admin panel (login is not admin) and the WiFi password (WPA2-PSK). The problem hasn't gone away. They reappear.
Question: what are these devices in my local area?
Suspicions: utility services such as virtual machines in the NAS (on the network recently, less than a month). But definitely no virtual machine has yet been launched by me there.