As far as I know this has always been this way (played beta a year ago and now since TU). Once you lid the lighthouse light, the town is under invasion forever.

The story behind it is that, you help the people escape. So the invaders "won" and get the town. It is a bit strange though cause even after you helped them escape, and took away the defenders, the invaders keep invading (instead of relishing in their conquered town).

I've seen a good amount of threads popping up bout this, but so far, ZOS didn't take any action.

Nerk wrote: »

Eh, but i've been going to normal bleakrock after doing the main quest and leaving the area for weeks, and everything was fine. It changed just now. Moreover, when i go there i cannot go back unless i use a wayshrine recall as i can't enter any building (crypt included) and the npc for the boat trip back isn't there.

Sounds like you were bugged, and it has since been fixed. Bleakrock is supposed to be always under attack after you leave.