Traffic from unassigned subnet?

[Kets_One]

Hi,

Today i noticed that suspicious traffic from LAN -> WAN was blocked by Q-Feeds (thanks Q-feeds).
What i cannot understand is where this traffic originated from: 192.168.90.100 (port 123).
This should be impossible, since the DHCP range that i use is 192.168.1.0/24.
No fixed IPs are assigned.
ARP Table does not show the source IP (192.168.90.100).
Hostname of the source IP is empty.

The destination was 94.16.122.152 (port 123).
While this may look as ordinary NTP traffic, the destination IP does not appear an NTP server (no response).
Also, why would the originating IP address be out of the DHCP range?
And why would the destination IP be on a Q-Feeds blocklist?

Is this a spoofing attempt? Is this legit?
What am i missing?
How to find out which client this originated from?

As a mitigation and while i am figuring this out I have:
- Blocked the ASN for the destination address in F/W;
- Allowed only 192.168.1.0/24 and 224.0.0.0/8 out from LAN into F/W.