Horizontal crack in the wall

Hello,

I am new here, I hope this is the right forum.
We have viewed a house that I would be very interested in buying. A prefabricated house Elk Magic 159, about 12 years old.
At the stairway landing between the ground floor and the basement there is a horizontal crack on the wall (not an exterior wall), which is not large but clearly visible. The realtor calls this a settlement crack.
Question: Is this a sign of a serious subsidence or can this happen sometimes?
The owner offers to repair it before selling. He is a construction contractor himself and has the craftsmen. I made a counteroffer, we do it ourselves (many craftsmen in the family), if the price can be adjusted a bit.
Thankful for any opinion,
Tobi

You would have to look exactly at what height this crack is. Maybe too little adhesive was applied right there. It was the same with us. Mesh was embedded and we hope that it is enough.

here several high-resolution photos with plenty of light would certainly be appropriate