Long timeouts for stale PPPoE connections

[#1]

No loss of sync just PPP session, which took nearly 9mins to re-connect to a different gateway , this has happened in the past also  when it was confirmed as being your side ,  I can switch gateways without such a long time out  even after a power cycle of the router which has an uptime of 52 Day(s) 7 Hour(s) so no loss of power to it either

[#2]

The long time it is because it was an untidy disconnect.  Something on the exchange side still thinks you are connected.  If you are using a TG582 there is a setting you can apply to prevent this.

[#3]

I use a Billion 7800 router, Exchange side, could be  possibly where the underlying cause is then, as it's unlikely to be between the FTTC cab and the modem
There again the "Termination by server side (NAS) Modem"  event  your side , doesn't really provide much info to pin point what was responsible, But looking at  the  ping monitors and there is one that mirrors the same disconnect  but at a slightly different time  
So this could indicate something plusnets side or a BT core link that supplies both our connections  My guess would be that the gateway shed some of it's load
a rudimentary load balance maybe