Fix some NPC and Corpse falling through the ground issues

zone/mob.cpp

@@ -113,7 +113,7 @@ Mob::Mob(const char* in_name,
 		tmHidden(-1),
 		mitigation_ac(0),
 		m_specialattacks(eSpecialAttacks::None),
-		fix_z_timer(1000),
+		fix_z_timer(300),
 		fix_z_timer_engaged(100)
 {
 	targeted = 0;
@@ -121,6 +121,8 @@ Mob::Mob(const char* in_name,
 	tar_vector=0;
 	currently_fleeing = false;
 
+	last_z = 0;
+
 	AI_Init();
 	SetMoving(false);
 	moved=false;