Unfortunately it is merely a math problem. Until the peg comes in contact there is no friction. After it is in contact there is friction, and if the geometry is just wrong enough "virtual forces" to oppose any force. Real matter (which bends) can't have this problem- it is from the rigid model. The non-reversaiblity is this flaw plus the fact there is no friction in the model prior to contact (so there is a non-reverisble feature in the model).