Strange door in Shivering Isles disappeared - cannot leave SI

[Reskal]

Hi,

as topic says i cannot leave SI anymore. I'm in the quests for Sheogorath actually, and doing the "Symbols of OfficE" where i have to redo Sheogorath's Staff.
The door is gone since 2 quests or so. I googled but found not good hint to get it back again, but i need to go visit the trainers and somewhen i really want to go back to Cyrodiil.
Can someone help me ?

[Skeleton Senpai]

During the quest "Retaking The Fringe" the map markers in the area are removed and will need to be rediscovered. Unless you mean that the door is physically no longer in the game world, you only need to manually walk back to where it is.

[Reskal]

ok will try that, thank you