[2021] [Unable to progress in a quest] An Eye for an Eye (Wrath of the Druids DLC)

Hi all,

Context:
I have started the quest "An Eye for an Eye" (from the Wrath of the Druids DLC) where I need to capture Konstantinos and carry him to Azar. I killed his complices, and defeated him on his ship.

The problem:
He is now kneeling at the very edge of his ship, waiting to be tied up. Unfortunately his back is towards the water. Every time I try to tie him up, Eivor falls into the water and cannot complete the task of tying him up.

Already tried the following:

• Stopped tracking the quest, followed another quest, travelled to another area (England), quit the game, started it again, came back to the area. His complices respawned, but Konstantinos is still in the same position on the very same place.
• Called my longship to park it in a way to prevent me falling down, didn't work: the longship is lower, so I am still falling down.
• Tried to load saved game: all auto-saves are after the problem occured. Manual save is too several hours played old.

I have screenshots available to illustrate the problem, but I couldn't attach them here.

Would you please help me how to solve this issue?

Thank you.