@Clive_A 

What do you mean with "Application Result feature"?
Searching for that term in the web interface of the ER7212PC, I do not get any result.
I tried to make a video as requested (see attached archive):
- See device having IP address 192.168.55.206 (this an address from the IP pool)

- Click on the device, click on 'Configure' - see the IP address, which is reserved for that device.

- Click on 'Apply', action confirmed.

- Click on 'Log' - see the new log entry.
- Click on 'Force provision' - action confirmed.

After a while the device gets the reserved IP address (see screen shot in attached archive).
If I did not click 'Force provision', the device would have kept the wrong IP address.

  @Clive_A 

Sorry, if I got you wrong - I thought, you want to see what happens, when I apply the (actually already configured) reservation to a device, which got an address from the ip pool instead, what is wrong. In the video shot you can see, that there was created a new log entry right after clicking 'Apply' (red counter badge increased from 115 to 116).

I do not have this 'Application Result' menu when I open the Device List (see screenshot attached).
The firmware of the ER7212PC seems to be not that old (see second screenshot).

I do agree - first of all the sync issue should be solved.

  @Clive_A Just to confirm that I tried making changes (remotely through the cloud) and specifically waiting for the "Succeeded" banner, and that seems to work with no Force Provision error, but I have to say that before the issue started for me, I would have been making multiple changes very quickly, so it does seem that the more recent versions of controller  firmware update the router more slowly. I will also be testing it when I have local access to the LAN.

I still have a major issue with the DHCP server not issuing addresses and also ignoring DHCP reservation rules and IP-to-MAC bindings, but I am away from the premises where the LAN is located, so I will start a separate thread about that on the forum when I'm back on-site next week.

  @Type17 

Hi!
Thank you for participating in this thread.
I hope, the more people participating, the more TP-Link understands the issue.

Could you, please, keep these two topics separated:
1. Sync between ER7212PC controller and router (this thread)
2. DHCP reservation issue (DHCP server ignores DHCP reservations)
Just for avoiding confusion...
Thank you!

  @gerba Of course, and thanks for the link to the other, already-running thread about ignoring DHCP rules.

Again:
Please keep these two topics separated: controller/router sync (this thread) and DHCP reservation (not this thread).
Thank you. 

  @Clive_A 

Could it be, that tests made last December, became outdated in the meantime?
Do you have the same firmware version (1.1.2 Build 20240102 Rel.50640) on your ER7212PC?

I'd like to emphasize the following concerning the ER7212PC (= main topic of this thread):
 

Everytime I change one single (!) setting, after applying it, the log entry is created right after a few seconds.

So obviously it's not a matter of changing several settings "within a very short time".

Actually the controller never synchronizes itself with the inbuilt router, but I always have to manually 'Force provision' after every single (!) setting change to really have it privisioned to the router.

By the way: How long can data transfer of a single setting value take within one and the same device? Electricity speed is nearly light speed. Even TCP communication takes just parts of a second for such data transfer. 

In the meantime I was told about some "a correlation issue" between 'IPsec Failover' in the VPN settings (which I never configured btw.) and the synchronization issue.
No idea, what that means, but maybe for someone out there this information is some base for an idea how to fix the synchronization issue?

Kind regards,
Gerald