Foundation basement window corner crack, how bad is it?

Hello Experts,

I have a two year old home. I hired and inspector to check the house with no significant finding. We noticed a corner window crack from the outside of the house, but he said since there is no leak inside the basement and the crack is not too wide it shouldn't be a concern. I couldn't check the basement inside because of the full insulation. A few weeks ago I decided to open up the insulation and found the the crack is coning from the corner of the window (see pics) and all the way down to the flood in a zig zag pattern (about 2mm wide on top, narrow at bottom). No sign of water damage. This is the house's second snowy winter and no leak so far. The basement has a sump pup.

I spoke to the builder and they are refusing to fix it because there is no signs of water damage, hence they say the crack in not going all the way through the wall (even tough it appears on both sides of the wall).

I attached a few pictures. Did anyone had to deal with this situation, how serious do you think it is? what can I do (crack does not seem structural, all doors and windows lock smoothly, no other crack at the house, only thing a lot of the corners in the rooms have a long fine crack, that is probably because there was no taped placed in the corners before painting).

Looking forward to your response, anything helps,

Thank you