This is just my own opinion on this dungeon bug, i'm no expert people.
Parties and other people – yeah, screw leveling up with others, carry all the weight in your back (if you can enter the dungeon tho).
I think having too much people; people who are also experiencing the bug, inside the dungeon at the same time may cause this bug to go on troll mode. I have noticed that this bug is not that picky when choosing what dungeon to choose, I made a series of test that I think supports this theory. I tried going alone or with someone, it’s still 50/50. But when I tried to “Reset the Dungeon” it works smoothly, with party or not. To put it simply, there’s a case that someone already had finished the dungeon at the exact time you go in; “but bro, I still can’t go inside the dungeon even if no one’s around?” From an artists’ perspective or even programmers, we have this thing we call rendering time. For artist it’s the time of process were 3D animations are being created and for programmers it’s the time of the code to activate (again im no expert). Lets’ say that it takes a minute to render the whole dungeon, in that 1 minute, there are 20 people that are trying to go inside the dungeon (just for the sake of the theory, just go with it). Some of those 20 players will experience the bug, while the others won’t. Why? It’s because of the rendering time. Every PC has its own time and every game has its own time. Some of those are the same, and some are not. So keep that in mind every time you go on a dungeon.
Unfinished missions – skipped missions that are trying to haunt you by not letting you get in a dungeon, initiate troll mode.
This one is a bit tricky but I really solved the dungeon bug with this one. When the Freyja server came up, I rushed in by leveling a Wizard of mine (when I say rushed, I mean seriously rushed, I didn’t do anything I just go for the missions). But one mission stopped me on my tracks; the mission after the saint was blessing the barrier? I tried so many times to enter the dungeon yet I kept on failing, that’s when I saw something weird. Before the Payon forest missions, there was Izlude missions. I skipped all the Izlude missions somehow and went straight to Payon Forest. Long story short, I finished all my Izlude missions; I mean all of them even the Kharas. After that, miraculously I finally entered the troll dungeon. I don’t have any solid proof for this one, but it worked for me so #YOLO.
Monsters – yes, monsters; those aggressive monsters that attack you for no valid reason, they are the ones that are seriously have the TROLL MODE.
Be aware of those annoying pieces of poop. Once they start to attack you when you are entering the dungeon, it would announce BATTLE START and you just stand there, inside the cold entrance, all alone, can’t speak, can’t cast a spell and forced to restart the game.
That concludes my theories and feel free to say your opinions.