My 2927 has worked fine for 2 years on Brsk broadband. They recently got acquired by YouFibre and since the migration last week WAN1 drops every 20 minutes then comes back on a minute later. (I hadn't changed any settings on the router.)
I have a static IP.

If I connect the Brsk supplied Technicolor router it is fine, see left hand side of graph. However as soon as I swapped to the 2927 the drops return, see right hand side.
I have tried cloning the MAC from the Technicolor onto WAN1 of the 2927, but no better.

When I look at the logs on the Draytek I can see that just before each drop it sends two DHCP requests.
The first request gets a response, but the second request is followed by a WAN1 drop.

I don't understand why the 2927 sends two requests sometimes, or why that results in the WAN dropping.
Can anyone offer any explanation or suggest troubleshooting steps?

 

I might try copying the MAC address of the Brsk supplied Technicolor router to the Draytek WAN (under WAN > Internet Access and then "Specify a MAC address").

It sounds like the YouFibre DHCP lease is (edit) 20  minutes and for some reason it won't renew with the Draytek but after an bit it will issue an address.

I assume you have left the ONT turned off for a few minutes.

After you have tried those two it might be having to contact YouFibre's support.....

After a bit of a search I came accross this very fine article.

https://www.aoakley.com/articles/2022-10-05-youfibre-technical.php

It's another vote for trying MAC address spoofing.