PC Quests disappearing from active quests list in journal

[Toshiro]

I have done a lot of searching, but been able to find anyone else having this problem.

Some quests just started, but not continued have disappeared from my journal after a while. I have the Legendary edition.
The ones missing:
-Speak to Aventus Arentino. Can't find the boy. Do I pick the lock of the house or what?
-Join the Dawnguard. Fort Dawnguard is still on the map.
-Travel to Solstheim. The ship is still in the Windhelm harbour.

I wanted to start the Dark Brotherhood quest, but could find it on my journal list anymore and noticed the Dawnguard and Dragonborn quest starts had gone, too. This was after many hours of play. I have finished the Main quest, Civil war, Thieves guild, Mages quest.

How did that happen?

 

[Mike Page]

Yes, he is inside
as for the other two, why wouldn't Fort Dawnguard and the ship be there? Did join go away? Do you have it selected as a mission you are currently working on?

 

[Toshiro]

Yes, he is inside
as for the other two, why wouldn't Fort Dawnguard and the ship be there? Did join go away? Do you have it selected as a mission you are currently working on?

I found Aventus inside. Creepy boy.

The Dawnguard and Dragonborn quests were not selected. They were in the list for some time, then disappeared.