@Marcel. 
I'm not in a position to downgrade router firmware at the moment, this is deployed in a business where they will lose money if they don't have internet. Their network is working completely fine at the moment, I just get the pleasure of receiving a notification every ten minutes that the router has disconnected. The issue is not the router firmware, I did not upgrade that. I upgraded the controller firmware. TP-Link needs to issue an updated/patched controller firmware that fixes this issue. Downgrading the router firmware isn't a solution, it's a temporary fix. Since I did not update the firmware of the router, and did not have this issue before updating the controller, I am concluding the issue is the controller firmware. 

  @Hank21 

can i use ER605(UN)_v2_2.1.0_Build 20230117 (Beta) but the version of my OC200 is just 5.7.6?

 when will the version 5.8.x be available for OC200?

  @Kash01976 I wouldn't hold my breath, Fae completely abandoned the Thread about the 7206 having DHCP issues, no word for weeks now, and no fixes for the broken junk we're still dealing with. At this point it's time for the lawyers to get involved, they broke our systems, and now it's time for them to pay for that :) I refuse to accept that my 7206 should be forced to run outdated firmware because they cannot get the basic features right in the new firmware.

When will v2_2.1.0 (or other)  be patched and released again?    It was quickly removed from TP-links's ER605 firmware download page the day the problems stating showing up on the forums.

  @Hank21 Does it fix the GRC Sheildup stealth mode failed issues?????? 

I need to know if the firmware for this ER605 V2 fix the GRC Sheildup stealth mode failed issues is really really fix!

@Fae 

I don't have PPoE ..... Mines pure Dynamic (FTTP NBN) and it's having a million and one issues now.  I was on Omada 5.5.7 on the OC200.  I updated to 5.7.6 I think it is.  It was fine until that.  Now it's dropping in and out, now it just plain says it's disconnected but the net still works. It failed to update some settings when I as adjusting them on the OC200 Omada panel and boom....... went to adopting, provisioning, got stuck on configuring..... then dropped, then stuck on adopting. I did a reset of it....... rejoined ....... took ages, went through and now it's messed up again. Come on TPLink. Seriously. Fix it. Fix Omada ....... PROPER QoS, IP Stats listed in Omada, Simple IP Blocking...... Stability!

I ended up messing around with it for AGES.......  trying to figure out what I wanted to do.  I tried removing the OC200 completely and reset everything, setting them all up standalone but ran into the issue of not being able to figure out how to get VPN working on the ER605, the EAP610 and EAP615 wouldn't run a 2.4+5G network with the same name and just randomly had issues.  Also the ER605 I found on that newer firmware even the BETA in standalone mode pretty much did the exact same thing as Omada......... it saves settings and hangs etc.  So I'd say the ER605 firmware is purely the issue.  

And this is BUSINESS GRADE stuff.  And you release this garbage?  Who's doing the testing........  100% TP Link fail.

In the end I went back to ER605 Firmware 2.01 and left Omada on 5.7.6 and it seems to be working fine.

I run a 172.16.x.x 255.255.0.0 network here.....  if TP Link see this.  Also a few IP's try breaking into the VPN, is there any VPN protection?  So eg.  If someone tries 10 times in 24 hours their IP gets blocked AUTOMATICALLY.

Weirdly they only try once an hour.

AGAIN...........  What you need to fix in the ER605 it dropping or pausing the connection when changing anything on it such as adding/removing port forwarding or ACL rules.  It should not be dropping connections when doing this.  It's very annoying having to announce the networks going offline for a second to make a small change.

Just upgraded and the GRC Shields up is reporting stealth mode.  So far so good.  There was some weirdness with admin access using the Vivaldi browser saying it was not supported, but all the sudden it seems to be working... wondering?

My ER605 is operating in standalone mode.

  @Hank21 Seems I just hit the problem with my ER605 v1 being stuck in Adopting. I have no remote availability now to upgrade or downgrade its firmware which is currently v1.2.3. Though I doubt that would even be an option if it's in Adopting mode.

I've never had this happen before until this firmware version. While we have internet connectivity I've lost any remote connectivity to it (which is how I actually found this problem) as none of the port forwarding settings are working. I'll have to physically power it off/on and hopefully re-adopts properly where I can then think about downgrading to one of the previous versions I've used without this issue.