I Found this bug while i was mad because i didnt get my re entry ticket from valtan back so i went in a abyss dungeon and tried what happend if u got once a re Entry ticket from mail and then if u dc again in the Same dungeon the second time u dont get the mail right away or never
TLDR since ppl had issues with re entry ticket i think the issue is since some people leave after G1 and then make a new party for G2 and go in again then somehow u Dcing u dont get the Re Entry Ticket back ( i think the system give u only 1 ticket)
Hopefully the dev can check it out if its true