IF i turn on multiple characters. like 4 chars. 1, 2 and 3 goes ok but when add 4th and online it, bot will D.c all other chars. and relogging work some of the chars but not for all when that bug comes. 
your case it same with me, in 2 month ago...
in my case, it caused by a error waypoint, so i decided to remake a waypoint. not all of waypoint, but only your waypoint error, in your case if you log your char in 4th TAB. all of your char disconnect, so i think you must remake waypoint in your char when you log in 4th TAB