Several plank piles are spawned incorrectly, dynamic event engine porobably always snapps them to the surface, and does not take other objects into accounting.
To fix this, you can spawn them with explicitly set Y atribute (that works for me when defining eventgroups [item will not snap and will keep it's innitial pitch = 0], so should also work for simple - single item events)
I have found these two, but there may be more wrongly spawning events here.
I believe same issue can happen at the lumber west of the map, north from Myshkino military tents ( ~ 920.63, 7618.59 )
[once I was checking it when first found this "bug", and if I remember right that place also had this issue]
Position: <12396.780273, 23.368374, 14327.218750> (this is approximated position of both pile events)