@MartinBer 

I am seeing the same thiing with an Archer AX1500 in Access Point mode.  I just discovered it yesterday and have not had a chance to troubleshoot.  The WAN port of the AX1500 renews the lease about every 30 seconds.  My DHCP server isc-dhcp-server and is set to a 6 hour lease.  All the other devices on the network honor that lease and renew at 3 hours (50% of lease time). I will post more if I figure anything out.

@MartinBer 

Yes, I have the latest firmware.

@MartinBer Is your device still renewing every 30 seconds?

I changed my TP-Link to a fixed IP address while I troubleshoot another problem.  I noticed the DHCP issue because my TP-Link would randomly reboot every couple days.  Since I changed to a fixed IP address on the AX1500 it has not rebooted.  I have to wait a couple weeks to make sure that the issue is fixed.  If it does fix it, I will contact TP-Link about the fast DHCP renewal because it might be related to the rebooting.

Reference: https://community.tp-link.com/en/business/forum/topic/199292

update: 2020-05-05 DHCP issue does not fix the rebooting. 

After many emails about this AX1500 issue with TP-Link support they stated the DHCP operation is a  "built-in mechanism which is not a bug to be fixed".  They call it "Smart DHCP".  It is the "mechanism that will keep checking if there's another DHCP server here in the period of 30s.The Smart DHCP is to help determine if the router should open AX1500's own DHCP server or not."

@Paul_S 

Now firmware version is 1.09, Im sure you are aware of that

I'm seeing this also, on an AX1500 with the latest firmware, 1.2.5 Build 20220117 Rel. 51845(4555).

I have the AX1500 DHCP server set to "off" (not "auto"), so I don't think it's a legit reason to renew the DHCP lease every 30 seconds to check if it needs to turn the DHCP server on.  Since it's disabled and should never start.  I suppose there is some value in knowing the DHCP server is functional for clients connected to the AP.  Perhaps the orange light would come on if it was down.

Still, it's flooding the router log with DHCP renewals.

@Kevin_Z Yes, the DHCP server on the AX1500 is set to "Off" and it still sends DHCP requests to the router every 30 seconds.  The AX1500 is set to "Access Point Mode" and the LAN setting on the AX1500 is set to "Dynamic IP."  The AX1500 has a cat-6 cable connected to the WAN port going to a gigabit switch that the Mikrotik router is also connected to.  The Mikrotik has a DHCP server.

So I would expect the AX1500 to get it's IP from the router, just not every 30 seconds, since the DHCP lease time on the router is 24 hours.