This is the same issue i had before but im coming back with a few weeks of testing and a better understanding of the issue hoping someone can help more.

I am currently crashing when attempting to enter Limsa upper and lower decks, New Gridania, and The Ruby Seas. There may be more but I haven't checked. Some of them seem to have slightly different rules for me when trying to log in.

Limsa lower and upper decks and new gridania seem to let me in occasionally, but Lower decks will sometimes crash anyway after a few moments. I have been able to enter more often in the middle of the night when there are less people. The ruby seas seem to crash every time without fail.

Finally this crashing seems to be only when im on the North American data center. I was able to enter the ruby seas on the Oceania data center. I haven't checked enough to see if it just crashes in different areas on that data center.

Support has already told me to open up ports 54992 through 54994, 55006 through 55007, and 55021 through 55040 on my router but it doesn't seem to have solved anything so far.