Keep disconnecting to login screen

I can't get through a single lab without crashing to login. On my second character and on the first it took over 4 hours to complete 1 lab because I kept DCing trying to complete it.

If you're going back to login screen and not crashing, it sounds like network instability to me. Could be on GGG's end, it could be on your ISP's end, or it could be on your end. I would suggest checking out Technical Support and there's a guide for running WINMTR which can help track where the issue lies. GGG will not be able to assist if it's not an issue on their end.