I cannot describe how frustrating this is. It happens to me a lot - unless I'm in a party with someone (who is either in the instance or just out in the world) I get booted. The other day I got so frustrated trying to complete LWS2 achievements that I 'leeched' a Silverwastes Squad, hoping no one would notice I wasn't in map and participating, just so I would be 'partied up' and the game wouldn't forget I was online mid-instance. They did notice, before I finished an instance, and of course - it booted me out and I lost credit for the achievement I'd worked for an hour. How is this fair to people who have to play solo 90% of the time??
Just now - I literally spent 45mins trying to complete LWS2 Seeds of Truth - No Refuge with the Challenge Mote, finally beat the boss without dying and I get to the Wynne/Faolin conversation at the end and it boots me out. Again. Came on here to vent (as this has happened to me for years) - to find that this thread is 22 pages and has been unresolved for years.
What's more frustrating - I'm not brilliant at the game, so I have to work hard for some of these achievements. I have limited play-time as I'm a mum to two kids under 3. I shouldn't get excited after finally doing something I was finding incredibly difficult to then be left heartbroken less than a minute later when I can tell the instance has stalled and is about to boot me out of the game again, wishing I wasn't playing alone.
It really really really sucks.