HI , thanks again to all. I've read your situation and you didn't loose sync. I continually do so, the cause and solution are right for you, unfortunately not for me, sigh! I have continually been trying things out as you can imagine and by turning off the wifi on the EE router I haven't had a reconnection/resync in 22 hours. The longest I've stayed up for months! So something "appears" to be causing the routers to resync via/because of the wifi. I've maintained a wifi network by connecting a 2nd router via ethernet, with DHCP turned off, and at a distance away. Shouldn't have to, as most people will only have the ISP provide modem/router/wifi "box" and not be able to split out the functions. I shouldn't have to, as this is only masks the problem but doesn't find the root cause to cure it. Time will tell if it actually does. Still, thanks very much for the suggestion and effort!

Just an update openreach visited. told him whole story and he went away to do a lift and sgift, although I had effectively had one when I changed ISP. He also found a different paie from the PCP cab to the base of the pole across the road. He said he had been down my street several times because of the cable ("not the best"). Before he arrived I played around with putting myHH5 with OPenWRt on because I knew I would get a DLM reset anyway and any messing I did would not drive my "record" down.( I had read that you could change your SNR and effectively up your line speed). After the "lift and shift" i did notice a considerably less rate of increasing FEC count and no CRC's errors. Then he did the pair change and it still stayed low. So a possible improvement there too. If you read my earlier post from today I had switched off the wifi in my EE router and had no resyncs for quite a few hours (novel). Well I split the wifi channels and put only the 5Ghz on. In the short time before OR arrived - no resyncs. I have done the same with my HH5 i.e. turned off the 2.4GHz wifi. Lets see if it was a problem with 2.4 Ghz devices causing the router to reboot. I have moved the 2.4 to a router that is connected by ethernet and is in a seperate room to allow older (non5Ghz capable devices) to connect) If any do cause that router (an old SKy routr with DHCP turned off, but giving me 2.4 and extending my wifi) then to reboot it will be that router and not my modem, so the DLM won't see line drops and act to drop my line speed. If it is 2.4GHz devices then it is down to bluetooth, microwaves (unlikely as I wasnt using it 12 times during the previous earlier hours), or other devices, wireless keyboards, mobile phones etc. The routers "shouldn't" reboot because of these just being around BUT maybe it's because there is just so many devices, that router got its Kn*****s in a twist and just resynced as its answer/cure-all response. We'll see.

Although you've already said you've tried a couple different devices, my advise is ditch the Vodafone junk.
1 of the worst ISP provided hubs I've come across.

Just an update openreach visited. told him whole story and he went away to do a lift and sgift, although I had effectively had one when I changed ISP.

Nobody visits the cabinet do to a lift and shift when you switch ISP.
It's all done remotely now.

As I suggested in an earlier post. Try switching off all your WIFI devices overnight but leave the router/modem on.

Check if any disconnects in the morning.

Testing all scenarios should narrow down the issues.

How many devices do you have connected via WIFI?

sorted , I Think ! The Openreach engineer changed the pair from the cabinet to the pole opposite my house. This brought down the FECS count rate. I couldn't switch off all wireless devices because there are so many people who visit evening and early morning and neighbours with devices-- these still caused it to resync. I think the real "CURE" was turning off the 2.4G frequency in the router. (split the Wifi and turn off the 2.4) Routers, 4 of them, should be able to cope but obviously didn't.The EE router worked for over 24 hrs without a resync after turning it off. Usually there are 15 resyncs a day which drives down my DLM. I put my BT HH5 with Openwrt installed and this stayed O.K. with the 2.4 off as well. By using a 2nd router connected via ethernet cable I can get this 2.4 back for older devices/ devices that are not 5G capable e.g Kindles. and extend my wireless network as well. For people who have a lot of resyncs & poor speed AND who don't need the 2.4G this may well be a solution. You shouldn't have to turn it off. The modem/router/wifi device maybe needs to handle problems without a crash/resync situation.

The "turning off" was to check if any reconnects happened and not as a cure.

One has to test all aspects in order to narrow the issue.