Syslog WiFi and New Neighbours

I have a Draytek 2820 with latest firmware and two SSID’s.

Over the last few years I’ve had new neighbours every 6 months’ish (Tenants).

My current neighbours have been in for roughly 6 weeks since which I seem to have a lot of activity 24hrs a day (Diagnostics – Traffic Graph) but there are no user access logs to match the data.

Is this activity my neighbours smart phones innocently trying to establish a connection on a regular basis or are my neighbours actively trying to hack in?

I reckon that there is approximately 67mb of unexplained data back and forth every day without log entries to account for it.

If you have WPA2 enabled (on all SSIDs) and they don't know your password, they shouldn't be able to send/receive data so 75Mb of data wouldn't just be connection attempts IMHO.

This wese my thoughts too but there are no entries in the log files, no devices active etc.

Is the router itself doing this!? DNS and or Time checks.

This situation has only occured after one of two possibilities, Firmware Upgrade or new neighbours which happened within a couple of days or so of each other. The Traffic Graph shows a very small amount of data in and out on a fairly regular basis 24hrs a day. Making a note of the approx time the events are taking place and looking in the log files nothing matches up.

The property is a Holiday let and when it's empty i still have data back and forth, events continue even when i change the passwords. I did once have guests who gave a previous neighbour the WiFi password, spotted this fairly quickly at the time and rectified the problem.

Is it possible that communication data between the router and my ISP is being recorded on the traffic graph but not being written to the log files?