Openreach FTTP (Aquiss / Entanet) PPPoE reconnect slow

I'm using a UDM-SE connected to the standard Huawei OpenReach ONT, on Aquiss 1Gig home service.

Had some issues around the default MTU breaking almost everything, they're all sorted now I've worked out how to (kludgilly) set the MTU to 1500/1508. Speed and latency seem great.

Every time I change a setting in the general firewall / WAN area of the UDM, it causes a PPP reconnect, which previously on FTTC has been fine. Now, it seems to be taking a good 5 minutes before it will allow a reconnect. I noticed the same when I tried my laptop connecting directly with PPPoE (Timeout waiting for PADO packet). It seems not to be timing out the old connection quick enough.

Is this me, Openreach or Aquiss, and is there any way around this? At the moment I still have a VM line for it to fail back to while its waiting, but that disapears at the end of the month.

It seems fairly common with other ISPs too: e.g.
https://forums.thinkbroadband.com/sky/t/4698443-re-s...
https://forums.thinkbroadband.com/sky/t/4721530-re-s...

I suggest the solution is: don't fiddle around with your WAN settings

However, it might also work better if you do a controlled shutdown of the PPPoE session. You could try:
- disable the WAN/PPPoE interface
- fiddle
- re-enable the WAN/PPPoE interface
and see if it re-establishes more quickly.

Ahh well as long as its not just me! Hope they all drop PPPoE, don't want to start that discussion again but I see no reason for it at all now!

Sadly no option to disable it cleanly.