After opening the access to the witch hunter's cave, I explored it and eventually reached the passage to Hiberheim through the lake.

As I did not finish the cave, I decided to finish it before and after a long period of adventuring I also decided to go to the End of time, store items, then do some shopping etc ...

In short: I took my time to ready to go to Hiberheim.

All this took me around 2 hours (real time).
Now I went back to the lake in the witch hunter cave and ... can't click it to teleport to Hiberheim.

Is this an intended feature or am I victim of a bug ?
Is there anything to do to activate the lake ?
I still have an old save, but I really do not want to spend again those 2 hours ...

If it is intended I do not get the point as at the beginning of Hiberheim there is a teleport, so anyway we could go there to activate this Hiberheim tp and then take the time to do stuff before continuing there ...