Traffic sniffing

I have a very strange thing going on in my house … spooky !
I use 6 2-channel Wifi dimmers (based on ESP8266) in my home automation.
Each 2-channel dimmer has it’s own IP address (of course).
Now, 1 of them has 1 channel that gets turned on in the middle of the night, but I don’t know why and how and by who.
In the morning I get up and sometimes this light is on … it always seems to happen overnight, never in the daytime …
So, 5 and a half dimmers are doing perfect (11 channels out of 12) and 1 is mysteriously switched on …
I checked the logs of my home automation on this device, I see all kinds of acivity from us switching this light on and off but there is no activity to confirm this mysterious sponanious ON command …
Is there a way to have PFsense sniff out the traffic to this dimmers IPaddres (LAN - and log this (I have PFsense logging “everything” to a Syslog server - synology NAS) for debugging purposes ?
If so, please tell me how to do this, and how to set it up … and how to setup the PFsense logging to monitor this in my NAS for later investigation ?

You can go to Diagnostics-> Packet Capture and filter just for and create a pcap file that you can download and place in Wireshark to see the traffic.