Could you explain more about the environmental conditions?

The area comes under sub-temperate zone with scanty rains and few months of dry periods @ kourosh vahadati

I could not understand the commentary in the video but the video was clear. Have you checked for insect damage and consequent weak point on the stem? I have seen borer attacks on succulent new growth of the season that can cause this type of damage. This is not a major problem on walnuts grown for edible nuts although the economic damage can be significant on trees grown for timber.