I cant find any info on it
Well, some of my characters just lost all their Guild rep and are back to Neutral standing after being Exalted since YEARS ago. Anyone else seeing that? Bug Ticket opened.
Checked a few of my toons ones i checked didnt drop rep, Hopefully they fix this issue but idk if they will restore your rep 
Hopefully they will/do guild rep is a pain if you dont got any quests to do